Validating PDF/UA compliance

PDF/UA in a Nutshell

A PDF document’s degree of accessibility is hard to determine at first glance. How, then, can you tell if and to what extent a PDF file meets the requirements of PDF/UA?

A reliable compliance test depends on at least two stages of validation: a programmatic test, which can be performed by a piece of software, and an interactive test carried out by a human. Dedicated validation tools will help the user perform the programmatic test. They test and show the extent to which the PDF document meets the standard’s purely technical requirements (including tag-based content structuring, alternative text for images, a document title) and uses the correct syntax to implement them. The semantic aspects of PDF/UA, however, cannot be tested in the same way. Is the reading order logical? Does the alternative text adequately represent the same information as the images to which it is attached? Do the header tags reflect their corresponding header levels? These and other questions can only be answered after evaluation and testing by a human user. Tools also exist to help the user perform these tests. Some of the more important validation tools are listed below.

One further test (which should be run on at least a random sample of all documents created) is to use the PDF document with a selection of current types of assistive technology. Regular users of the technology can be enlisted to test the documents in this way; in most cases, however, anyone can in principle perform a useful test with assistive technology to confirm the readability of the PDF document.

Screenshot - PDF Accessibility Checker 2

The Access For All foundation’s PDF Accessibility Checker 2.0 (PAC 2) software supports all automatically-checkable PDF/UA criteria. 

One very simple option here is to use the free Windows screen reader program NVDA. A user can quickly get to grips with the core functions of the software in order to test how well people with disabilities can actually use an existing (ideally fully PDF/UA-compliant) document.

Program Developer Validation function Validation criteria
Acrobat XI Adobe ­Systems Quick test
  • First impression of document quality
  • Not a comprehensive test
Complete accessibility test, input/output report
  • Numerous functions, some of them heuristic
  • Not a complete PDF/UA compliance test
  • Access restrictions (password protection, copy-protection etc.) do not affect accessibility
  • Document is not just a PDF file made up of images alone
  • Document is a tagged PDF
  • Logical reading order assigned to the document
  • Text language is defined
  • Document title is displayed in the window title bar
  • Bookmarks are present in large documents
  • Sufficient colour contrast within the document
PAC 2.0 (free) “Access For All” foundation Validates accessibility, structural view, preview, PAC test report
  • Currently the only program which fully supports all automatically-testable PDF/UA criteria
  • Numerous heuristic tests to support interactive testing
CommonLook PDF NetCentric Technologies Display and test a number of tagged PDF properties

  • Reading order
  • Correct tag usage
  • Heuristic checking for common errors
  • Checks table structure
callas pdfGoHTML (free) callas software Structured visualisation
  • Converts tagged PDF to structured HTML view
  • Fast interactive test for sensible reading order, correct tag usage, appropriate alternative text and other semantic elements
  • Useful addition to automatic tests

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About PDF Association

Founded in 2006 as the PDF/A Competence Center, the PDF Association exists to promote the adoption and implementation of International Standards for PDF technology.

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