Article: 9788 of comp.text.sgml
Newsgroups: comp.text.sgml
From: Liz McQuarrie <>
Subject: PDF and the Visually Disabled
Message-ID: <>
Organization: Adobe Systems Incorporated
Date: Thu, 6 Jul 1995 14:53:12 GMT

There have been discussions on this newsgroup
about issues regarding the accessibility of
PDF for the visually disabled. The attached
document outlines the issues and Adobe's
plans for making PDF accessible.  (This document
was also posted to comp.text.pdf.)



June 30, 1995 
Liz McQuarrie 
Adobe Systems Incorporated

Adobe's Portable Document Format, the native file format of the Adobe Acrobat 
products, is a final form description language for documents that is not tied 
to any operating system or application.  PDF provides the document layout 
richness of Adobe PostScript and allows publishers to retain the look and 
feel of their publication.  On the World Wide Web, PDF is becoming 
increasingly popular for documents that need the layout richness that 
HTML currently does not provide.  Corporations are also using PDF to 
disseminate electronic documents over corporate networks, via e-mail, or on 

For the visually disabled, however, there are currently some accessibility 
issues associated with PDF and the use of Adobe Acrobat viewers (Reader and 
Exchange) for viewing PDF files.  This document describes Adobe's plans for 
making both the Adobe Acrobat viewing products and the PDF file format 
accessible for the visually disabled.

Overview of Acrobat and PDF Accessibility Plans

Adobe has the following plans to make PDF and the Adobe Acrobat products 
accessible to the visually disabled:

	Offer an Accessibility Plug-in for Adobe Acrobat on Microsoft  
	Windows (available in late 1995).  The plug-in will allow users to access 
	Acrobat for Windows through cooperation with Windows screen-reading 
	programs, as well as output formatted ASCII that is compatible with 
	alternative output devices, such as Braille printers.

	Enhance the PDF format and Adobe Acrobat for Logical Document Structure 
	(available in 1996).  Adobe currently has an active project under way to 
	add knowledge of a document's logical structure to the PDF file format and 
	to build solutions based on these extensions.   For visually disabled 
	users, the PDF structure project will deliver several accessibility 

Adobe Acrobat Viewers and Microsoft Windows Screen 

Screen-reader programs allow the visually disabled to interact with the 
Windows interface by interpreting what is happening on the display and 
outputting that information to speech synthesis or refreshable Braille output 
devices.  Although screen-reader programs for DOS have been around for many 
years, screen-reader programs for Microsoft Windows that provide reasonable 
performance and functionality have only been introduced in the last year 
or so.  

Limited Screen Model and PDF Documents 

The delay in the availability of Windows screen readers is due to a number of 
factors.  First, it is quite an intellectual challenge to present what is 
happening on the Windows display to a visually disabled person in a way that 
allows the user to be productive.  This is because with Windows (or any 
other GUI-based operating system), there may be multiple applications open 
simultaneously, each of which has a title bar, menus and several child 
windows for their data. Each application also has many visual controls to 
present: icons, scroll bars, and dialog boxes that include check boxes, 
buttons and list boxes.  

To keep track of what is happening on the screen, Windows screen readers build 
what is referred to as an off-screen model in memory, and then allow the user 
to navigate through the screen model.  For example, from the screen reader, 
the user can select a particular application window to interact with.  Then 
once an application is selected, the user can navigate and read text in the 
window.  Reading text usually involves using commands like "Next Line," 
which reads the next line down the page, and "Previous Word," which reads the 
word immediately to the left of the current word.  

The current screen models for Windows for handling the text that is in an 
application-specific window are very similar to the models developed for DOS.  
These models can typically only represent text in simple documents, where the 
document contains a single column of text that flows left to right and top 
to bottom on the page.  They cannot properly represent documents with more 
complex layout, such as a multi-column newspaper or documents with text 
that is not horizontal, like a tax form that contains vertical labels.   
When the screen-reader program encounters such complex layout in an 
application, it will likely make mistakes.  For example, in a multi-column 
document, the screen reader would probably read the first line in the first 
column, followed by the first line in the second column, running the columns 
together as if they were on the same line.  Because many PDF documents have 
such rich layout , the use of Windows screen readers with Acrobat on these 
documents will not produce useful output for the visually disabled person. 

For the future, Adobe is participating in discussions with Microsoft and 
Windows screen reader vendors regarding a new Application Programming 
Interface to screen readers in Windows that hopefully will more fully 
support complex documents. 

Conflicts Between the Acrobat Viewers and the Screen 

The second factor that has delayed development of capable Windows screen-
reader programs is that there are no easy operating system "hooks" (or entry 
points) in the current operating system (Windows 3.1) for developers to use to 
build the screen readers.  (Note that Microsoft is currently adding such 
hooks to Windows 95.)  The net result of this oversight is that developers 
of Windows screen readers have each independently invented techniques for 
capturing screen state for alternative output devices in often incompatible 

Additionally, the Windows version of the Adobe Acrobat viewer really pushes 
the Windows environment technically in order to render visually beautiful 
documents with fonts that are very close to the author's original fonts.
This fact often causes the Acrobat viewer products to be incompatible with 
many of the screen readers.  Screen readers are not able to read any text 
in the Acrobat document windows, regardless of the layout.

The Adobe Acrobat Solution for Windows for the Visually 

To make PDF documents accessible to visually disabled users of Microsoft 
Windows, Adobe is developing a special plug-in for Acrobat.   (A "plug-in" is 
a piece of software that works with the standard Acrobat product and enhances 
its capability.)  This plug-in is called the "Accessibility Plug-in". 

The Accessibility Plug-in for Acrobat will present an alternative view of the 
open document in a separate window. This view will contain the text in as 
close to reading order as possible, including presenting multi-column 
documents as a single column, and "straightening" all non-horizontal text. 
This alternative view will use only those text attributes that screen readers
currently understand, such as bold and italic. 

The Accessibility Plug-in will interact with the primary Acrobat document 
display in such a way as to make interaction as seamless as possible and will 
allow the use of all standard Acrobat features, such as access to annotations 
and hypertext links.  Additionally, the Accessibility Plug-in will allow 
users to export from PDF to ICADD-compliant ASCII, as well as to formatted 
ASCII.  ICADD (International Committee for Accessible Document Design) has 
proposed using a set of tags based on SGML (Standard Generalized Markup 
Language) with documents to enable them to work with alternative output 
devices, such as Braille printers.   

A Beta version of the Accessibility Plug-in for Windows will be available in 
early fall, and will be distributed free of charge through a number of 
channels, including the World Wide Web.  The Accessibility Plug-in will work 
with both the Acrobat Reader product, which is free, as well as Acrobat 

Adobe Acrobat and Other Platforms

There are currently two other platforms that have screen reading programs 
available: DOS and the Macintosh.  (Screen readers for X-Windows systems on 
UNIX are still under development.) DOS screen readers only work with the text
display of DOS.  A third-party organization is currently contracting out the
development of a Acrobat Viewer for DOS that will work in text mode.  The DOS
viewer will be available in the public domain.  Note that this viewer is text
mode only, and is not related to the Adobe Acrobat 1.0 Viewer for DOS, which 
is a graphics mode viewer.  

The Apple Macintosh has not been a popular platform for the visually disabled.
This is probably due to the fact that many of the screen reader software 
vendors started working with DOS, and then grew into Windows when it became 
available.  There is, therefore, only one screen reading program available 
for the Mac: outSpoken from Berkeley Systems.  Unfortunately, outSpoken for 
the Mac currently has a bug when operated with Acrobat that causes Acrobat 
to exit when the user attempts to read the document.  Berkeley Systems 
intends to fix this bug in their next release.   When an updated outSpoken,
however, is available, it will also have problems with complex documents that 
contain multiple columns and/or rotated text.  Plans for an Accessibility 
Plug-in for Acrobat on the Macintosh are still being formulated. 

Extensions to PDF for Document Logical Structure

The second area of interest regarding PDF and the visually disabled concerns 
document logical structure. ("Logical Structure" refers to the organization 
of the document, such as title page, chapters, sections, subsections.)
Although standard ASCII may be adequate for disabled access to short 
documents, access to longer, more complex documents is greatly enhanced by 
an understanding of the document's logical structure.  Many advocates for the 
visually disabled feel that documents based on SGML are best suited for 
accessibility because of SGML's strength in representing document logical 
structure in a portable way.  Documents based on SGML, however, continue to 
be a small percentage of those that a visually disabled person may encounter 
on a day-to-day basis. 

Adobe currently has an active project under way to add knowledge of a 
document's logical structure to the PDF file.  This project will benefit all 
Acrobat users -- there are several important problems that can be solved when
the logical structure knowledge of the document is available.  An example:  
the ability to search for documents that contain words in specific chapters 
or headings.  For visually disabled users, the PDF Structure project will 
deliver several accessibility solutions, which are described below. 

Document  Structure Knowledge Leads to a Better Accessibility Plug-in

The Accessibility Plug-in to the Acrobat Reader will be greatly enhanced by 
knowledge of the document's logical structure.  To begin with, by knowing a 
document's logical structure, the Accessibility Plug-in will be able to do a
much better job of displaying the document in reading order. Consider, for
example, a PDF document that is a newspaper, where the first page contains 
the beginnings of three articles, each of which is continued on a separate 
page.  With a knowledge of the document structure, the Accessibility Plug-in
will be able to follow a single article from beginning to end, much like a 
sighted person would flip the newspaper page to continue the article until 

Second, many navigational features for both sighted and non-sighted 
individuals can take advantage of the document's logical structure. An 
example: next and previous section links.  

Finally, the plug-in can do an even better job of exporting to an 
ICADD-compliant tagged ASCII file by supporting a richer set of ICADD tags 
(ICADD ASCII can then be used with alternative output devices).

Availability of Structure in PDF

A shipping date for products from Adobe that include document logical 
structure in PDF is currently scheduled for calendar year 1996.  	

Comments or Questions?

Liz McQuarrie
Adobe Systems Incorporated