How to Create Accessible Acrobat PDF files

By Paul Bohman
Updated April 21, 2002

I. Introduction

When people talk about the accessibility of Adobe Acrobat, or PDF files (PDF stands for "Portable Document Format"), they are usually referring to the accessibility of Acrobat to screen readers. Before diving into that topic in depth, I just want to remind people that blindness is not the only disability to be concerned with when developing Web content. The other major disability types to be concerned with are mobility impairments, hearing impairments, and cognitive impairments. It's also important to remember that not all visual disabilities are blindness. Those with low vision have needs of their own. Let's look at how to make PDF files accessible to these disability types.

II. Mobility Impairments

• Don't make hot spots too small. Of course, the phrase "too small" is relative, and it is true that people can enlarge the document, thus enlarging the hot spots within the document, but use good judgement here. The smaller the link, the more difficult it will be for someone with limited fine muscle control to click on the link.

III. Hearing Impairments

• Provide transcripts for multimedia. If you embed multimedia objects with sound in your PDF documents, you will exclude both the deaf and the deaf-blind if you do not provide a transcript.
• Provide synchronized captions for video. People who are deaf need this if the video does not make sense when the sound is turned off.

IV. Cognitive Impairments

• Use clear and simple language. In other words, write well. The better you write, the better you will be understood.
• Make the document accessible to screen readers. Not all people with cognitive disabilities use or benefit from hearing the content read to them, but some do. In order for the content to be read out loud, it must be accessible to screen readers.

V. Low Vision

• Ensure that there is enough contrast.
• Ensure that any information conveyed with color is conveyed equally well when color is not available. You may want to use an asterisk or some other textual cue in addition to the color in order to convey the information.

VI. Blindness and Screen Reader Accessibility

Okay, now we're going to look at making PDF files accessible to screen readers. Before the release of Acrobat 5.0, it was not even possible to talk about this topic. PDF files were not accessible to screen readers in any meaningful way. Now it is possible to expose the text in PDF files to screen readers . . . but that's not the end of the story. Adobe has not created a magical product that suddenly makes all accessibility errors disappear. Much like HTML, PDF files must be created with accessibility in mind. Otherwise, the files will be nearly as inaccessible as before Acrobat 5.0 came around. The bad news is that it usually takes more work to make PDF accessible than it does to make HTML accessible. Still, it can be done. Let's look at the methods for making accessible PDF files.

Conditions upon which PDF accessibility to the blind is based:

Conditions that the document must meet:

1. The document must contain real text.
2. The document must be in Tagged PDF format.*
3. The document must be marked up for accessibility.*

(*only possible in Acrobat 5.0, full version).

Conditions that the user must meet:

1. The user must have either JAWS or Window Eyes.
2. The user must have Acrobat 5.0 or greater.

A Closer Look at What the Developer Must Do

Rule 1: The document must contain real text.

PDF files are not so much documents as they are captured bits of information that tell a printer how to print a page. The format is a graphical representation of information. As the PDF format has matured, Adobe has incorporated into it other, more document-like features. Acrobat has evolved to the point that the text within Acrobat files can now be made accessible to screen readers and other assistive devices.

There are two common types of PDF documents:

1. Scanned images of text.
2. Text files (from word processors, desktop publishing software, etc.) that have been converted into PDF files.

If your PDF document was converted directly from a word processing program, then you've met this criteria. If you have scanned in pages of text, then you have created a document which is inaccessible to screen readers. As you might guess, scanned images of text are completely useless to a blind person. I suppose you could create an alt attribute for a whole page of text, but that would be more work than it's worth, and is definitely an abuse of the alt text concept. A more practical solution for existing scanned PDF documents is to use an OCR (Optical Character Recognition) program to convert the image into real text. Adobe provides an OCR utility for Acrobat with the full version (not the free reader). There's no getting around this rule. To make the document accessible to screen readers, you have to have real text.

Rule 2: The document must be in Tagged PDF format.

Some of the simpler, linear, no-frills documents are accessible to screen readers even if tagged PDF is not used, but, to be honest, if your document is this simple, I have to question why you are using PDF in the first place. HTML would probably suffice, and would be easier for your users, especially those with disabilities. Most PDF documents will need to be in a tagged PDF in order to be accessible. There are three ways to generate tagged PDF:

1. Use a Microsoft Office product to generate the document, then convert it to PDF.
2. Run the "Make Accessible" plug-in on existing PDF documents, then clean it up.
3. The hard way: create the tags yourself.

1. Using Microsoft Office to produce the document

Adobe has built-in support for converting Microsoft Office documents directly into tagged PDF format. If you're using anything other than Microsoft Office, then you'll have to use one of the two other methods listed below.

2. Running the "Make Accessible" plug-in

This may not be installed your configuration of Acrobat 5.0. If it isn't installed, you can download the Make Accessible Plug-in from Adobe's Web site. It's easy to use. You just open the file, go to Document | Make Accessible. It runs a little script, then it's done with it's part, though for you it is merely the beginning (see Rule 3 below).

3. Creating the Tags Yourself

This isn't the first thing that you want to try to do, especially if you're new to PDF accessibility. When and if you get to this stage, though, use the Adobe resources listed at the bottom of this page as reference manuals.

Rule 3: The document must be marked up for accessibility:

Does this sound familiar? HTML has to be marked up for accessibility in order to be accessible. PDF files must also be marked up for accessibility. Even if you have real text, and if it's tagged PDF, it's rather useless unless it's marked up well.

In Office:

Important: When converting from Office, only well-marked-up Office documents will produce well-marked-up PDF files!

This means that you must use real headings (not just large, bold fonts), bullets, numbered lists and other structural tags in the original Office document. If you don't, then no special tags will be created when the document is converted into PDF. Garbage in, garbage out. For many people, this means learning how to use the structural elements within Word, because too many of us don't pay much attention to the "style" options in word processors. We pay attention to the visual output. This has to change in order to make the content accessible and usable in screen readers.

Important: You must add alternative text in the Office file in order for the alternative text to be converted into the PDF format.

To do this in Word XP in Windows, right-click on the image, select "format picture" then the "Web" tab, then add the alternative text. Other versions of Word have similar functionality.

When using the "Make Accessible Plug-in":

Important: You must touch-up the file, or you're still less than halfway to an accessible document in many cases.

It would be nice if this plug-in could always recognize the headers of a document, even when the author used bolded, large regular text, but it can't. It would also be nice if this plug-in could automatically add alt text for all of the images, but it can't. These are things that you must do yourself. This is the hard part. You must go to Windows | Tags within the Acrobat menus. This will bring up a window that lists all of the tags in the document and displays them in a hierarchical tree structure. You will likely notice some recognizable tags, such as <p> and <table> but will see other, less familiar tags that don't convey any information to you. You'll probably have to fix some of these tags by converting them to <p>, <h1> or whatever the appropriate tag should be. It takes some time to learn this interface, and it's not nearly as friendly as working with HTML in a text editor, but it can be done. Plan on spending some time learning how to manipulate the tag names, order, and content.

Adobe has two good resources for learning how to do this:

• HTML or PDF booklet: "How to Create Accessible Adobe PDF Files" .
• PDF booklet: "Advanced Techniques for Creating Accessible Adobe PDF Files".

Guidelines For All Disability Types

Here are a few guidelines that apply to PDF files just as much as they do to HTML:

• Supply text for all non-text elements.
• Information conveyed with color must be available when color is unavailable.
• Use clear and simple language.
• For data tables, identify row and column headers.
• Associate data cells with their headers.
• Provide transcripts for all multimedia content.
• Provide captions for video.
• Provide sufficient contrast.
• Use headers and other structural markup.
• Avoid flickering.
• Clearly identify the target of each link
• Put form labels next to their controls.
• Specify the expansion of each abbreviation or acronym in a document where it first occurs.

If you violate any of these principles, then you are creating potential problems.

VII. Conclusion

It's wonderful that Adobe has made it possible to make PDF files that are accessible to users of screen readers. Remember though, that only two screen readers on the market, JAWS and Window Eyes, currently support accessible PDF files. This still leaves out the users of other screen readers. It's always a good idea to provide an HTML version in addition to the PDF, even if the PDF is created with accessibility in mind.

Top of Page || Return to Tutorials List