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Are Your Digital Documents Web Friendly?: Making Scanned Documents Web Accessible


Abstract and Figures

The Internet has greatly changed how library users search and use library resources. Many of them prefer resources available in electronic format over traditional print materials. While many documents are now born digital, many more are only accessible in print and need to be digitized. This paper focuses on how the Colorado State University Libraries creates and optimizes text-based and digitized PDF documents for easy access, downloading, and printing.
Content may be subject to copyright.
Are Your Digital
Web Friendly?:
Making Scanned
Documents Web
The Internet has greatly changed how
library users search and use library
resources. Many of them prefer resources
available in electronic format over tradi-
tional print materials. While many docu-
ments are now born digital, many more
are only accessible in print and need to be
digitized. This paper focuses on how the
Colorado State University Libraries cre-
ates and optimizes text-based and digitized
PDF documents for easy access, download-
ing, and printing.
o digitize print materials,
we normally scan originals,
save them in archival digital
formats, and then make them Web-
accessible. There are two types of
print documents, graphic-based and
text-based. If we apply the same tech-
niques to digitize these two different
types of materials, the documents
produced will not be Web-friendly.
Graphic-based materials include
archival resources such as his-
torical photographs, drawings,
manuscripts, maps, slides, and post-
ers. We normally scan them in color
at a very high resolution to capture
and present a reproduction that is
as faithful to the original as possible.
Then we save the scanned images in
TIFF (Tagged Image File Format) for
archival purposes and convert the
TIFFs to JPEG (Joint Photographic
Experts Group) 2000 or JPEG for Web
access. However, the same practice is
not suitable for modern text-based
documents, such as reports, jour-
nal articles, meeting minutes, and
theses and dissertations. Many old
text-based documents (e.g., aged
newspapers and books), should be
Yongli ZhouTutorial
files for fast Web delivery as access
files. For text-based files, access files
normally are PDFs that are converted
from scanned images.
“BCR’s CDP Digital Imaging Best
Practices Version 2.0” says that the
master image should be the highest
quality you can afford, it should not
be edited or processed for any specific
output, and it should be uncom-
This statement applies to
archival images, such as photographs,
manuscripts, and other image-based
materials. If we adopt the same
approach for modern text documents,
the result may be problematic. PDFs
that are created from such master files
may have the following drawbacks:
Because of their large file size,
they require a long download
time or cannot be downloaded
because of a timeout error.
They may crash a user’s com-
puter because they use more
memory while viewing.
They sometimes cannot be
printed because of insufficient
printer memory.
Poor print and on-screen view-
ing qualities can be caused by
background noise and bleed-
through of text. Background
noise can be caused by stains,
highlighter marks made by
users, and yellowed paper from
aged documents.
The OCR process sometimes
does not work for high-resolu-
tion images.
Content creators need to spend
more time scanning images at a
high resolution and converting
them to PDF documents.
Web-friendly files should be
small, accessible by most users,
full-text searchable, and have good
treated as graphic-based material.
These documents often have faded
text, unusual fonts, stains, and col-
ored background. If they are scanned
using the same practice as modern
text documents, the document cre-
ated can be unreadable and contain
incorrect information. This topic is
covered in the section “Full-Text
Searchable PDFs and Troubleshooting
OCR Errors.”
Currently, PDF is the file format
used for most digitized text docu-
ments. While PDFs that are created
from high-resolution color images
may be of excellent quality, they can
have many drawbacks. For exam-
ple, a multipage PDF may have a
large file size, which increases down-
load time and the memory required
while viewing. Sometimes the down-
load takes so long it fails because a
time-out error occurs. Printers may
have insufficient memory to print
large documents. In addition, the
Optical Character Recognition (OCR)
process is not accurate for high-
resolution images in either color or
grayscale. As we know, users want
the ability to easily download, view,
print, and search online textual docu-
ments. All of the drawbacks created
by high-quality scanning defeat one
of the most important purposes of
digitizing text-based documents:
making them accessible to more
This paper addresses how
Colorado State University Libraries
(CSUL) manages these problems and
others as staff create Web-friendly
digitized textual documents.
Topics include scanning, long-time
archiving, full-text searchable PDFs
and troubleshooting OCR problems,
and optimizing PDF files for Web
Preservation Master
Files and Access Files
For digitization projects, we normally
refer to images in uncompressed TIFF
format as master files and compressed
Yongli Zhou is Digital Repositories
Librarian, Colorado State University
Libraries, Colorado State University, Fort
Collins, Colorado
factors that determine PDF file size.
Color images typically generate the
largest PDFs and black-and-white
images generate the smallest PDFs.
Interestingly, an image of smaller file
size does not necessarily generate a
smaller PDF. Table 1 shows how file
format and color mode affect PDF
file size.
The source file is a page contain-
ing black-and-white text and line art
drawings. Its physical dimensions
are 8.047" by 10.893". All images were
scanned at 300 dpi.
CSUL uses Adobe Acrobat
Professional to create PDFs from
scanned images. The current ver-
sion we use is Adobe Acrobat 9
Professional, but most of its features
listed in this paper are available
for other Acrobat versions. When
Acrobat converts TIFF images to a
PDF, it compresses images. Therefore
a final PDF has a smaller file size than
the total size of the original images.
Acrobat compresses TIFF uncom-
pressed, LZW, and Zip the same
amount and produces PDFs of the
same file size. Because our in-house
scanning software does not support
TIFF G4, we did not include TIFF G4
test data here. By comparing simi-
lar pages, we concluded that TIFF
G4 works the same as TIFF uncom-
pressed, LZW, and Zip. For example,
if we scan a text-based page as black-
and-white and save it separately in
TIFF uncompressed, LZW, Zip, or
G4, then convert each page into a
PDF, the final PDF will have the same
file size without a noticeable quality
difference. TIFF JPEG generates the
smallest PDF, but it is a lossy format,
so it is not recommended. Both JPEG
and JPEG 2000 have smaller file sizes
but generate larger PDFs than those
converted from TIFF images.
1. Use TIFF uncompressed or LZW
in 24 bits color for pages with
color graphs or for historical doc-
2. Use TIFF uncompressed or LZW
compress an image up to 50 per-
cent. Some vendors hesitate to
use this format because it was
proprietary; however, the patent
expired on June 20, 2003. This
format has been widely adopted
by much software and is safe to
use. CSUL saves all scanned text
documents in this format.
TIFF Zip: This is a lossless
compression. Like LZW, ZIP
compression is most effective for
images that contain large areas of
single color.
TIFF JPEG: This is a JPEG file
stored inside a TIFF tag. It is a
lossy compression, so CSUL does
not use this file format.
Other image formats:
JPEG: This format is a lossy com-
pression and can only be used for
nonarchival purposes. A JPEG
image can be converted to PDF
or embedded in a PDF. However,
a PDF created from JPEG images
has a much larger file size com-
pared to a PDF created from TIFF
JPEG 2000: This format’s file
extension is .jp2. This format
offers superior compression per-
formance and other advantages.
JPEG 2000 normally is used for
archival photographs, not for
text-based documents.
In short, scanned images should
be saved as TIFF files, either with
compression or without. We recom-
mend saving text-only pages and
pages containing text and/or line art
as TIFF G4 or TIFF LZW. We also
recommend saving pages with photo-
graphs and illustrations as TIFF LZW.
We also recommend saving pages
with photographs and illustrations as
TIFF uncompressed or TIFF LZW.
How Image Format and Color
Mode Affect PDF File Size
Color mode and file format are two
on-screen viewing and print quali-
ties. In the following sections, we will
discuss how to make scanned docu-
ments Web-friendly.
There are three main factors that affect
the quality and file size of a digitized
document: file format, color mode,
and resolution of the source images.
These factors should be kept in mind
when scanning text documents.
File Format and Compression
Most digitized documents are
scanned and saved as TIFF files.
However, there are many different
formats of TIFF. Which one is appro-
priate for your project?
TIFF: Uncompressed format. This
is a standard format for scanned
images. However, an uncom-
pressed TIFF file has the largest
file size and requires more space
to store.
TIFF G3: TIFF with G3 compres-
sion is the universal standard
for faxs and multipage line-art
documents. It is used for black-
and-white documents only.
TIFF G4: TIFF with G4 com-
pression has been approved as
a lossless archival file format
for bitonal images. TIFF images
saved in this compression have
the smallest file size. It is a stan-
dard file format used by many
commercial scanning vendors. It
should only be used for pages
with text or line art. Many scan-
ning programs do not provide
this file format by default.
TIFF Huffmann: A method for
compressing bi-level data based
on the CCITT Group 3 1D fac-
simile compression schema.
TIFF LZW: This format uses a
lossless compression that does
not discard details from images.
It may be used for bitonal, gray-
scale, and color images. It may
to be scanned at no less than 600
dpi in color. Our experiments show
that documents scanned at 300 or
400 dpi are sufficient for creating
PDFs of good quality. Resolutions
lower than 300 dpi are not recom-
mended because they can degrade
image quality and produce more
OCR errors. Resolutions higher than
400 dpi also are not recommended
because they generate large files with
little improved on-screen viewing
and print quality. We compared PDF
files that were converted from images
of resolutions at 300, 400, and 600
dpi. Viewed at 100 percent, the differ-
ence in image quality both on screen
and in print was negligible. If a page
has text with very small font, it can
be scanned at a higher resolution to
improve OCR accuracy and viewing
and print quality.
Table 2 shows that high-resolu-
tion images produce large files and
require more time to be converted
into PDFs. The time required to
combine images is not significantly
different compared to scanning time
and OCR time, so it was omitted.
Our example is a modern text docu-
ment with text and a black-and-white
Most of our digitization projects
do not require scanning at 600 dpi;
300 dpi is the minimum requirement.
We use 400 dpi for most documents
and choose a proper color mode for
each page. For example, we scan our
theses and dissertations in black-and-
white at 400 dpi for bitonal pages. We
scan pages containing photographs
or illustrations in 8-bit grayscale or
24-bit color at 400 dpi.
Other Factors that Affect
PDF File Size
In addition to the three main fac-
tors we have discussed, unnecessary
edges, bleed-through of text and
graphs, background noise, and blank
pages also increase PDF file sizes.
Figure 1 shows how a clean scan can
largely reduce a PDF file size and
cover. The updated file has a file
size of 42.8 MB. The example can
be accessed at http://hdl.handle
.net/10217/3667. Sometimes we scan
a page containing text and photo-
graphs or illustrations twice, in color
or grayscale and in black-and-white.
When we create a PDF, we com-
bine two images of the same page to
reproduce the original appearance
and to reduce file size. How to opti-
mize PDFs using multiple scans will
be discussed in a later section.
How Image Resolution
Affects PDF File Size
Before we start scanning, we check
with our project manager regarding
project standards. For some funded
projects, documents are required
in grayscale 8 bits for pages with
black-and-white photographs or
grayscale illustrations.
3. Use TIFF uncompressed, LZW,
or G4 in black-and-white for
pages containing text or line art.
To achieve the best result, each
page should be scanned accordingly.
For example, we had a document with
a color cover, 790 pages containing
text and line art, and 7 blank pages.
We scanned the original document
in color at 300 dpi. The PDF created
from these images was 384 MB, so
large that it exceeded the maximum
file size that our repository software
allows for uploading. To optimize
the document, we deleted all blank
pages, converted the 790 pages with
text and line art from color to black-
and-white, and retained the color
Table 1. File format and color mode versus PDF file size
File Format Scan Specifications TIFF Size (KB) PDF Size (KB)
TIFF Color 24 bits 23,141 900
TIFF LZW Color 24 bits 5,773 900
TIFF ZIP Color 24 bits 4,892 900
TIFF JPEG Color 24 bits 4,854 873
JPEG 2000 Color 24 bits 5,361 5,366
JPEG Color 24 bits 4,849 5,066
TIFF Grayscale 8 bits 7,729 825
TIFF LZW Grayscale 8 bits 2,250 825
TIFF ZIP Grayscale 8 bits 1,832 825
TIFF JPEG Grayscale 8 bits 2,902 804
JPEG 2000 Grayscale 8 bits 2,266 2,270
JPEG Grayscale 8 bits 2,886 3,158
TIFF Black-and-white 994 116
TIFF LZW Black-and-white 242 116
TIFF ZIP Black-and-white 196 116
Note: Black-and-white scans cannot be saved in JPEG, JPEG 2000, or TIFF JPEG formats.
Many PDF files cannot be saved
as PDF/A files. If an error occurs
when saving a PDF to PDF/A, you
may use Adobe Acrobat Preflight
(Advanced > Preflight) to identify
problems. See figure 2.
Errors can be created by non-
embedded fonts, embedded images
with unsupported file compression,
bookmarks, embedded video and
audio, etc. By default, the Reduce
File Size procedure in Acrobat
Professional compresses color images
using JPEG 2000 compression. After
running the Reduce File Size pro-
cedure, a PDF may not be saved as
a PDF/A because of a “JPEG 2000
compression used” error. According
to the PDF/A Competence Center,
this problem will be eliminated in the
second part of the PDF/A standard—
PDF/A-2 is planned for 2008/2009.
There are many other features in new
PDFs; for example, transparency and
layers will be allowed in PDF/A-
However, at the time this paper
was written PDF/A-2 had not been
portable, which means the file cre-
ated on one computer can be viewed
with an Acrobat viewer on other
computers, handheld devices, and on
other platforms.
A PDF/A document is basically a
traditional PDF document that fulfills
precisely defined specifications. The
PDF/A standard aims to enable the
creation of PDF documents whose
visual appearance will remain the
same over the course of time. These
files should be software-independent
and unrestricted by the systems used
to create, store, and reproduce them.
The goal of PDF/A is for long-term
archiving. A PDF/A document has
the same file extension as a regular
PDF file and must be at least compat-
ible with Acrobat Reader 4.
There are many ways to cre-
ate a PDF/A document. You can
convert existing images and PDF
files to PDF/A files, export a doc-
ument to PDF/A format, scan to
PDF/A, to name a few. There are
many software programs you can
use to create PDF/A, such as Adobe
Acrobat Professional 8 and later ver-
sions, Compart AG, PDFlib, and PDF
Tools AG.
simultaneously improve its viewing
and print quality.
1. Unnecessary edges: Crop out.
2. Bleed-through text or graphs: Place
a piece of white or black card
stock on the back of a page.
If a page is single sided, use
white card stock. If a page is
double sided, use black card
stock and increase contrast ratio
when scanning. Often color or
grayscale images have bleed-
through problems. Scanning a
page containing text or line art
as black-and-white will eliminate
bleed-through text and graphs.
3. Background noise: Scanning a
page containing text or line art
as black-and-white can elimi-
nate background noise. Many
aged documents have yellowed
papers. If we scan them as color
or grayscale, the result will be
images with yellow or gray back-
ground, which may increase PDF
file sizes greatly. We also recom-
mend increasing the contrast for
better OCR results when
scanning documents
with background colors.
4. Blank pages: Do not
include if they are not
required. Blank pages
scanned in grayscale or
color can quickly increase
file size.
PDF and Long-
Term Archiving
PDF, short for Portable
Document Format, was
developed by Adobe as a
unique format to be viewed
through Adobe Acrobat view-
ers. As the name implies, it is
Table 2. Color Mode and Image Resolution vs. PDF File Size
time (sec.)
OCR time
PDF size
color 600 100 N/A* 16,498 2,391
color 400 25 35 7,603 1,491
color 300 18 16 5,763 952
grayscale 600 36 33 6,097 2,220
grayscale 400 18 18 2,888 1370
grayscale 300 14 12 2,240 875
B/W 600 12 18 559 325
B/W 400 10 10 333 235
B/W 300 8 9 232 140
*N/A due to an OCR error
able. This option keeps the origi-
nal image and places an invisible
text layer over it. Recommended
for cases requiring maximum
fidelity to the original image.
This is the only option used by
2. Searchable Image: Ensures that
text is searchable and selectable.
This option keeps the original
image, de-skews it as needed,
and places an invisible text layer
over it. The selection for downs-
ample images in this same dia-
log box determines whether the
image is downsampled and to
what extent.
The downsam-
pling combines several pixels
in an image to make a single
larger pixel; thus some informa-
tion is deleted from the image.
However, downsampling does
not affect the quality of text or
line art. When a proper setting
is used, the size of a PDF can be
significantly reduced with little
or no loss of detail and precision.
3. ClearScan: Synthesizes a new
Type 3 font that closely approxi-
mates the original, and preserves
the page background using a
low-resolution copy.
The final
PDF is the same as a born-dig-
ital PDF. Because Acrobat can-
not guarantee the accuracy of
manipulate the PDF document for
accessibility. Once OCR is properly
applied to the scanned files, how-
ever, the image becomes searchable
text with selectable graphics, and one
may apply other accessibility features
to the document.
Acrobat Professional provides
three OCR options:
1. Searchable Image (Exact): Ensures
that text is searchable and select-
Full-Text Searchable
PDFs and Trouble-
shooting OCR Errors
A PDF created from a scanned piece
of paper is inherently inaccessible
because the content of the docu-
ment is an image, not searchable text.
Assistive technology cannot read
or extract the words, users cannot
select or edit the text, and one cannot
Figure 1. PDFs Converted from different images: (a) the original PDF converted from a
grayscale image and with unnecessary edges; (b) updated PDF converted from a black-
and-white image and with edges cropped out; (c) screen viewed at 100 percent of the
PDF in grayscale; and (d) screen viewed at 100 percent of the PDF in black-and-white.
Dimensions: 9.127” X 11.455”
Color Mode: grayscale
Resolution: 600 dpi
PDF: 1,051 KB
Dimensions: 8” X 10.4”
Color Mode: black-and-white
Resolution: 400 dpi
PDF: 61 KB
Figure 2. Example of Adobe Acrobat 9
but at least users can read all text,
while the black-and-white scan con-
tains unreadable words.
Troubleshoot OCR Error 3:
Cannot OCR Image Based
The search of a digitized PDF is
actually performed on its invis-
ible text layer. The automated OCR
process inevitably produces some
incorrectly recognized words. For
example, Acrobat cannot recognize
the Colorado State University Logo
correctly (see figure 6).
Unfortunately, Acrobat does not
provide a function to edit a PDF
file’s invisible text layer. To manu-
ally edit or add OCR’d text, Adobe
Acrobat Capture 3.0 (see figure 7)
must be purchased. However, our
tests show that Capture 3.0 has many
drawbacks. This software is compli-
cated and produces it’s own errors.
Sometimes it consolidates words;
other times it breaks them up. In
addition, it is time-consuming to add
or modify invisible text layers using
Acrobat Capture 3.0.
At CSUL, we manually add
searchable text for title and abstract
pages only if they cannot be OCR’d
by Acrobat correctly. The example in
Troubleshoot OCR Error 2:
Could Not Perform
Recognition (OCR)
Sometimes Acrobat gener-
ates an “Outside of the Allowed
Specifications” error when process-
ing OCR. This error is normally
caused by color images scanned at
600 dpi or more.
In the example in figure 4, the
page only contains text but was
scanned in color at 600 dpi. When
we scanned this page as black-
and-white at 400 dpi, we did not
encounter this problem. We could
also use a lower-resolution color scan
to avoid this error. Our experiments
also show that images scanned in
black-and-white work best for the
OCR process.
In this article we mainly discuss
running the OCR process on modern
textual documents. Black-and-white
scans do not work well for historical
textual documents or aged newspa-
pers. These documents may have
faded text and background noise.
When they are scanned as black-
and-white, broken letters may occur,
and some text might become unread-
able. For this reason they should be
scanned in color or grayscale. In fig-
ure 5, images scanned in color might
not produce accurate OCR results,
OCRed text at 100 percent, this
option is not acceptable for us.
For a tutorial on to how to make
a full-text searchable PDF, please see
appendix A.
Troubleshoot OCR Error 1:
Acrobat Crashes
Occasionally Acrobat crashes during
the OCR process. The error message
does not indicate what causes the
crash and where the problem occurs.
Fortunately, the page number of the
error can be found on the top short-
cuts menu. In figure 3, we can see the
error occurs on page 7.
We discovered that errors are
often caused by figures or diagrams.
For a problem like this, the solution is
to skip the error-causing page when
running the OCR process. Our initial
research was performed on Acrobat
8 Professional. Our recent study
shows that this problem has been
significantly improved in Acrobat 9
Figure 3. Adobe Acrobat 8 Professional
crash window
Figure 4. “Could not perform recognition
(OCR)” error
Figure 5. An aged newspaper scanned in color and black-and-white
Aged Newspaper Scanned in Color
Aged Newspaper Scanned in
a very light yellow background. The
undesirable marks and background
contribute to its large file size and
create ink waste when printed.
Method 2: Running Acrobat’s
Built-In Optimization
Acrobat provides three built-in pro-
cesses to reduce file size. By default,
Acrobat use JPEG compression for
color and grayscale images and
CCITT Group 4 compression for
bitonal images.
Optimize Scanned PDF
Open a scanned PDF and select
Documents > Optimize Scanned PDF.
A number of settings, such as image
quality and background removal, can
be specified in the Optimize Scanned
PDF dialog box. Our experiments
show this process can noticably
degrade images and sometimes even
increase file size. Therefore we do not
use this option.
Reduce File Size
Open a scanned PDF and select
Documents > Reduce File Size. The
Reduce File Size command resa-
mples and recompresses images,
removes embedded Base-14 fonts,
and subset-embeds fonts that were
left embedded. It also compresses
document structure and cleans up
elements such as invalid bookmarks.
If the file size is already as small
as possible, this command has no
After process, some files
cannot be saved as PDF/A, as we
discussed in a previous section. We
also noticed that different versions of
Acrobat can create files of different
file sizes even if the same settings
were used.
PDF Optimizer
Open a scanned PDF and select
Advanced > PDF Optimizer. Many
settings can be specified in the PDF
Optimizer dialog box. For example,
we can downsample images from
sections, we can greatly reduce
a PDF’s size by using an appro-
priate color mode and resolution.
Figure 9 shows two different ver-
sions of a digitized document. The
source document has a color cover
and 111 bitonal pages. The origi-
nal PDF, shown in figure 9 on the
left, was created by another univer-
sity department. It was not scanned
according to standards and pro-
cedures adopted by CSUL. It was
scanned in color at 300 dpi and has
a file size of 66,265 KB. We exported
the original PDF as TIFF images,
batch-converted color TIFF images
to black-and-white TIFF images, and
then created a new PDF using black-
and-white TIFF images. The updated
PDF has a file size of 8,842 KB. The
image on the right is much cleaner
and has better print quality. The file
on the left has unwanted marks and
figure 8 is a book title page for which
we used Acrobat Capture 3.0 to man-
ually add searchable text. The entire
book may be accessed at http://hdl
Optimizing PDFs for
Web Delivery
A digitized PDF file with 400 color
pages may be as large as 200 to 400
MB. Most of the time, optimizing
processes may reduce files this large
without a noticeable difference in
quality. In some cases, quality may
be improved. We will discuss three
optimization methods we use.
Method 1: Using an
Appropriate Color Mode and
As we have discussed in previous
Original Logo Text OCRed by Acrobat
Figure 6. Incorrectly recognized text sample
Figure 7. Adobe Acrobat capture interface
Figure 8. Image-based text sample
grayscale. A PDF may contain pages
that were scanned with different
color modes and resolutions. A PDF
may also have pages of mixed reso-
lutions. One page may contain both
bitonal images and color or grayscale
images, but they must be of the same
The following strategies were
adopted by CSUL:
1. Combine bitmap, grayscale,
and color images. We use gray-
scale images for pages that con-
tain grayscale graphs, such as
black-and-white photos, color
images for pages that contain
color images, and bitmap images
for text-only or text and line art
2. If a page contains high-definition
color or grayscale images, scan
that page in a higher resolution
and scan other pages at 400 dpi.
3. If a page contains a very small
font and the OCR process does
not work well, scan it at a higher
resolution and the rest of docu-
ment at 400 dpi.
4. If a page has both text, color,
or grayscale graphs, we scan it
twice. Then we modify images
using Adobe Photoshop and
combine two images in Acrobat.
In figure 10, the grayscale image
has a gray background and a true
reproduction of the original photo-
graph. The black-and-white scan has
a white background and clean text,
but details of the photograph are
lost. The PDF converted from the
grayscale image is 491 KB and has
nine OCR errors. The PDF converted
from the black-and-white image is
61KB and has no OCR errors. The
PDF converted from a combination
of the grayscale and black-and-white
images is 283 KB and has no OCR
The following are the steps used
to create a PDF in figure 10 using
1. Scan a page twice—grayscale
Optimizer can be found at http://
Method 3: Combining
Different Scans
Many documents have color covers
and color or grayscale illustrations,
but the majority of pages are text-
only. It is not necessary to scan all
pages of such documents in color or
a higher resolution to a lower reso-
lution and choose a different file
compression. Different collections
have different original sources,
therefore different settings should
be applied. We normally do sev-
eral tests for each collection and
choose the one that works best for
it. We also make our PDFs compat-
ible with Acrobat 6 to allow users
with older versions of software to
view our documents. A detailed
tutorial of how to use the PDF
Figure 9. Reduce file size example
Figure 10. Reduce file size example: combine images
ea53e41001031ab64-7757.html (accessed
Mar. 3, 2010).
3. Ted Padova Adobe Acrobat 7 PDF
Bible, 1st ed. (Indianapolis: Wiley, 2005).
4. Olaf Drümmer, Alexandra Oettler,
and Dietrich von Seggern, PDF/A in a
Nutshell—Long Term Archiving with PDF,
(Berlin: Association for Digital Document
Standards, 2007).
5. PDF/A Competence Center,
“PDF/A: An ISO Standard—Future
Development of PDF/A,” http://www. (accessed
July 20, 2010).
6. PDF/A Competence Center,
“PDF/A—A new Standard for Long-
Term Archiving,”
(accessed July 20, 2010).
7. Adobe, “Creating Accessible PDF
Documents with Adobe Acrobat 7.0: A
Guide for Publishing PDF Documents for
Use by People with Disabilities,” 2005,
(accessed Mar. 8, 2010).
8. Adobe, Recognize Text in
Scanned Documents,” 2010, http://
-B993-159299574AB8.w.html (accessed
Mar. 8, 2010).
9. Ibid.
10. Ibid.
11. Adobe, “Reduce File Size by Saving,”
(accessed Mar. 3, 2010).
the other 76 pages as grayscale and
black-and-white. Then we used the
procedure described above to com-
bine text pages and photographs.
The final PDF has clear text and cor-
rectly reproduced photographs. The
example can be found at http://hdl
Our case study, as reported in this
article, demonstrates the importance
of investing the time and effort to
apply the appropriate standards and
techniques for scanning and optimiz-
ing digitized documents. If proper
techniques are used, the final result
will be Web-friendly resources that are
easy to download, view, search, and
print. Users will be left with a posi-
tive impression of the library and feel
encouraged to use its materials and
services again in the future.
1. BCR’s CDP Digital Imaging Best
Practices Working Group, “BCR’s CDP
Digital Imaging Best Practices Version
2.0,” June 2008,
(accessed Mar. 3, 2010).
2. Adobe, “About File Formats and
Compression, 2010, http://livedocs
and black-and-white.
2. Crop out text on the grayscale
scan using Photoshop.
3. Delete the illustration on the
black-and-white image using
4. Create a PDF using the black-
and-white image.
5. Run the OCR process and save
the file.
6. Insert the color graph. Select
Tools > Advanced Editing >
TouchUp Object Tool. Right-
click on the page and select Place
Image. Locate the color graph in
the Open dialog, then click Open
and move the color graph to its
correct location.
7. Save the file and run the Reduce
File Size or PDF Optimizer pro-
8. Save the file again.
This method produces the small-
est file size with the best quality,
but it is very time-consuming. At
CSUL we used this method for some
important documents, such as one of
our institutional repository’s show-
case items, Agricultural Frontier to
Electronic Frontier. The book has 220
pages, including a color cover, 76
pages with text and photographs,
and 143 text-only pages. We used
a color image for the cover page
and 143 black-and-white images for
the 143 text-only pages. We scanned
Appendix A. Step-by-Step Creating a Full-Text Searchable PDF
In this tutorial, we will show you how to create a full-text searchable PDF using Adobe Acrobat 9 Professional.
Creating a PDF from a Scanner
Adobe Acrobat Professional can create a PDF directly from a scanner. Acrobat 9 provides five options: Black and White
Document, Grayscale Document, Color Document, Color Image, and Custom Scan. The custom scan option allows you to
scan, run the OCR procedure, add metadata, combine multiple pages into one PDF, and also make it PDF/A compliant.
To create a PDF from a scanner, go to File > Create PDF > From Scanner > Custom Scan. See figure 1.
At CSUL, we do not directly create PDFs from scanners because our tests show that it can produce fuzzy text and it
is not time efficient. Both scanning and running the OCR process can be very time consuming. If an error occurs during
these processes, we would have to start over again. We normally scan images on scanning stations by student employees
or outsource them to vendors. Then library staff will perform quality
control and create PDFs on seperate machines. In this way, we can work
on multiple documents at the same time and ensure that we provide
high-quality PDFs.
Creating a PDF from Scanned Images
1. From the task bar select Combine > Merge Files into a single PDF >
From Multiple Files. See figure 2.
2. In the Combine Files dialog, make sure the Single PDF radio button
is selected. From the Add Files dropdown menu select Add Files.
See figure 3.
3. In the Add Files dialog, locate images and select multiple images by
holding shift key, and then click Add Files button.
4. By default, Acrobat sorts files by file names. Use Move Up and Move
Down buttons to change image orders and use the Remove button
to delete images. Choose a target file size. The smallest icon will
produce a file with a smaller file size but a lower image quality PDF,
and the largest icon will produce a high image quality PDF but with
a very large file size. We normally use the default file size setting,
which is the middle icon.
5. Save the file.
At this point, the PDF is not full-text searchable.
Making a Full-Text Searchable PDF
A PDF document created from a scanned piece of paper is inherently
inaccessible because the content of the document is an image, not
searchable text. Assistive technology cannot read or extract the words,
users cannot select or edit the text, and one cannot manipulate the PDF
document for accessibility. Once optical character recognition (OCR)
is properly applied to the scanned files, however, the image becomes
searchable text with selectable graphics, and one may apply other acces-
sibility features to the document.
Adobe Acrobat Professional provides three OCR options, Searchable
Image (Exact), Searchable Image, and Clean Scan. Because Searchable
Image (Exact) is the only option that keeps the original look, we only
use this option.
To run an OCR procedure using Acrobat 9 Professional:
1. Open a digitized PDF.
2. Select Document > OCR text recognition > Recognize text using
3. In the Recognize Text dialog, specify pages to be OCRed.
4. In the Recognize Text dialog, click the Edit button in the Settings sec-
tion to choose OCR language and PDF Output Style. We recommend
the Searchable Image (Exact) option. Click OK. The setting will be
remembered by the program and will be used until a new setting is
Sometimes a PDF’s file size increases greatly after an OCR process. If
this happens, use the PDF optimizer to reduce its file size.
Figure 2. Merge files into a single PDF
Figure 3. Combine Files dialog
Figure 1. Acrobat 9 Professional’s Create PDF
from Scanner Dialog
... Currently, journal articles, books, monographs and other scientific electronic resources can be published and viewed online in various formats, such as PDF [3], HTML, EPUB, ODT. Traditionally, the most common and used format in the majority of scientific publications is PDF, because of the preserved printed format and the property protection capability, although there is an effort towards adopting the new version of EPUB format (EPUB version 3 at ...
Full-text available
A major requirement for electronic publishing systems is the availability of rich and intuitive mechanisms that enhance the user experience of viewing and searching online electronic documents such as books, monographs and journal papers. This work concerns a set of infrastructural components and their utilization for the creation of related coherent services and features for end users. We present a set of sophisticated platforms, tools and mechanisms that have been employed in real-life cases for implementing document viewing and full-text search features, shared among application instances of various types. Challenges encountered and the provided solutions are discussed.
... And one hopes that somewhere, among the many patrons of the archive, a spark of the imagination that according to Albert Einstein himself "is more important than knowledge…" [ 22 ] might be lit. 22 "Imagination is more important than knowledge. Knowledge is limited. ...
Full-text available
Purpose – The purpose of this paper is to present the organizational and technological processes and strategic choices that led to the successful digitization project of the Albert Einstein Archives. Design/methodology/approach – This is a case study of the major challenges that were associated with the project. These include: the integration of the archives in the academic environment; the management of a project of such magnitude within the university organization and between different stakeholders and the technological aspects of the project and user experience. Findings – A digitization project requires not only the archival staff expertise but also information specialists, IT staff, analysts and usually the digitization staff for processing the archival material. Finding the common language between all the professionals involved as well as building a good strategic plan are the keys to a successful project. Research limitations/implications – The planning and implementation of such a project requires a significant budget, manpower project management, hardware, software and intra- and inter-organizational cooperation and coordination. Originality/value – The phenomenon of digitizing unique and exclusive archival data by universities is becoming an innovative contribution of hidden goods to the public at large. This paper offers strategic insights for the planning of similar digitizing projects, particularly in an academic environment.
As more institutions continue to work with large and diverse type of content for their digital repositories, there is an inherent need to evaluate, prototype, and implement user-friendly websites -regardless of the digital file size, format, location or the content management system in use. This article aims to provide an overview of the need and current development of Document Viewers for digitized objects in DSpace repositories -including a local viewer developed for a newspaper collection and four other viewers currently implemented in DSpace repositories. According to the DSpace Registry, 22% of institutions are currently storing "Images" in their repositories and 21% are using DSpace for non-traditional IR content such as: Image Repository, Subject Repository, Museum Cultural, or Learning Resources. The combination of current technologies such as Djatoka Image Server, IIP Image Server, DjVu Libre, and the Internet Archive BookReader, as well as the growing number of digital repositories hosting digitized content, suggests that the DSpace community will probably benefit with an "out-of-the-box" Document Viewer, especially one for large, high-resolution, and multi-page objects.
Recognize Text in Scanned Documents
  • Adobe
Adobe, "Recognize Text in Scanned Documents," 2010, http:// Standard/WS2A3DD1FA-CFA5-4cf6-B993-159299574AB8.w.html (accessed Mar. 8, 2010). 9. Ibid.
Olaf Drümmer, Alexandra Oettler, and Dietrich von Seggern, PDF/A in a Nutshell—Long Term Archiving with PDF
  • Bible
Bible, 1st ed. (Indianapolis: Wiley, 2005). 4. Olaf Drümmer, Alexandra Oettler, and Dietrich von Seggern, PDF/A in a Nutshell—Long Term Archiving with PDF, (Berlin: Association for Digital Document Standards, 2007).
Creating Accessible PDF Documents with Adobe Acrobat 7.0: A Guide for Publishing PDF Documents for Use by People with Disabilities
  • Adobe
Adobe, "Creating Accessible PDF Documents with Adobe Acrobat 7.0: A Guide for Publishing PDF Documents for Use by People with Disabilities," 2005, accessibility/pdfs/acro7_pg_ue.pdf (accessed Mar. 8, 2010).
Reduce File Size by Saving
  • Adobe
Adobe, "Reduce File Size by Saving," 2010, Acrobat/9.0/Standard/WS65C0A053
About File Formats and Compression
  • Adobe
Adobe, "About File Formats and Compression," 2010, http://livedocs