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.
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||
|Complete accessibility test, input/output report||
|PAC 2.0 (free)||“Access For All” foundation||Validates accessibility, structural view, preview, PAC test report||
|CommonLook PDF||NetCentric Technologies||Display and test a number of tagged PDF properties||
|callas pdfGoHTML (free)||callas software||Structured visualisation||