PDF Accessibility
Defining Acrobat PDF Accessibility

Defining PDF Accessibility

The appropriate use of PDF files is a hotly debated topic, both inside and outside the field of web accessibility. Some people would argue that there is no place for PDF files, while others suggest that appropriately prepared PDF's are basically as accessible as HTML. We think the truth lies somewhere in-between. PDF files do have their place—displaying documents that print exactly as the author intends.

In order for a PDF to be truly accessible two conditions must be met:

  1. The author must create a well structured, correctly tagged, PDF.
  2. The reader must be able to correctly configure his or her accessibility preferences in Adobe Reader.

Both of these conditions will be discussed in this tutorial.

Remembering the Needs of All Users

As with HTML, you need to know what kinds of issues people with disabilities might encounter when reading PDF files. When people talk about the accessibility of Adobe Acrobat, or PDF files, they are usually referring to the accessibility of Acrobat to screen readers, but screen reader users are not the only people who should be considered when creating accessible PDF files. It is important to remember that not everyone with a disability is blind. You should also consider the needs of individuals with motor disabilities, hearing disabilities, cognitive disabilities or low vision. Let's look at some general guidelines for making PDF files accessible to people with other types of disabilities.

Motor disabilities

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 judgment here. The smaller the link, the more difficult it will be for someone with limited fine muscle control to click on the link.

Hearing disabilities

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.

Cognitive disabilities

Use clear and simple language. In other words, write well. The better you write, the better you will be understood by everyone, not just those with cognitive disabilities.

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.

Low vision

Ensure that there is enough contrast in the PDF document.

Ensure that any information conveyed with color is conveyed equally well when color is not available. You may want to use a textual cue in addition to the color in order to convey the information.

Blindness and screen reader accessibility

Before the release of Acrobat 5.0, 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 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 about. The bad news is that it usually takes more work to make PDF files accessible than it does to make HTML files accessible. Still, it can be done.

Two Approaches to Accessibility

Although Adobe is doing a better job of removing accessibility barriers from their product, HTML is still the preferred web format by the majority of users with disabilities.

Important

There are two approaches to making PDF content accessible:

  1. Approach #1: Provide an alternative HTML version of the PDF file (either instead of or in addition to the PDF file).
  2. Approach #2: Make the PDF file natively accessible, by creating a tagged PDF file with all of the appropriate accessible markup.

If an HTML equivalent is more accessible than a PDF, it may be more appropriate to eliminate the PDF files altogether and concentrate instead on making the content accessible in an HTML format. This isn't always an option, but in many cases it is worth considering.

Creating accessible tagged PDF files will make PDF files accessible to standard screen readers which support tagged PDF (like JAWS and Window Eyes). This circumvents the need for end users to learn how to use Adobe's embedded speech synthesizer. It is not always easy to make PDF files that are directly accessible to screen readers. Documents with complex layouts can be extremely difficult, if not impossible, to convert into an accessible PDF file, due to the fact that the content does not linearize correctly. It can also be very challenging to make documents with extensive charts or with embedded videos accessible.

WebAIM is an initiative of:
Center for Persons with Disabilities (CPD) Utah State University