PDF Accessibility Quick Checks
PDF Quick Checks
Generally, PDF files are not created with accessibility in mind. There are several methods to check a PDF file for accessibility as well as make changes to the PDF to meet accessibility guidelines. Some "Quick Checks" you can perform on your PDF document to see if it is accessible are:
- Checking for Text versus Image
- Checking for Presence of Text Equivalents
- Checking for PDF Tags
- Checking Reading Order
- Using Acrobat Read Out Loud feature
About PDF Files and Accessibility (from http://www.webaim.org/techniques/acrobat/)
Before discussing the accessibility of PDF files, it is important to distinguish between Adobe, Acrobat and PDF. Sometimes you will hear them used interchangeably, but they are not the same.
- Adobe is a company; they are the creators of Acrobat.
- Acrobat is a tool for creating, editing and viewing PDF files.
- PDF is a format or type of document. It stands for Portable Document Format. The PDF format was created by Adobe.
A good comparison to Adobe, Acrobat, and PDF is Microsoft, Word, and doc. When people talk about "accessible" PDF files, they usually mean "tagged" PDF files, even though there is more to an accessible PDF than tags. PDF tags provide a structured, textual representation of the PDF that is presented to screen readers. They exist for accessibility purposes only and have no visible effect on the PDF file.
HTML tags and PDF tags often use similar tag names and organization structures, but they really are quite different. For one thing, it is impossible to insert PDF tags in "code" view like you can with HTML.
Structure of a PDF File
An Accessible PDF File is made up of three different “layers” that must be in synch with one another.
Visual Layer (also referred to as the Physical Layer)
This is what you would associate as a “PDF File”. It is the version that would exist if you were to print out the PDF in a hard copy.
Content Layer (also referred to as the Text Layer)
This layer contains the textual information that is associated with the Visual Layer. In an accessible PDF, the reading order of the Content Layer mimics the order implied by the Visual Layout of the document.
Tags Layer
The Tags Layer contains the PDF tagging structure (similar to HTML markup for a webpage) that is used by assistive technology.
