Automated PDF accessibility checkers won’t tell you much, if anything, about issues affecting people with dyslexia or colour blindness

18 August 2021 | Ted Page

It may sound harsh to say so, but using only an automated PDF accessibility checker and nothing else to evaluate the accessibility of your PDFs may be more of a box-ticking exercise than a serious method of ensuring that your documents are actually accessible.


The limitations of automated testing

With a few caveats, automated accessibility checkers are reasonably good at identifying the sorts of issues that impact negatively on screen reader users.

Those caveats include that all automated checkers routinely fail to pick up on many actual problems as well as reporting things as errors that just aren’t. There are also substantial differences between checkers, so which one should you believe?

The biggest limitation of all?

But far more seriously than the above limitations is the fact that it’s just not possible for automated checkers to check for almost all of the issues that affect people with dyslexia or people with colour blindness. Both of these groups are likely to significantly outnumber screen reader users amongst your potential readers.

Audience sizes

According to the RINB, as of 2017 there were around 350,000 blind and partially sighted people in the UK. This is the group from which most screen reader users are likely to come.

By contrast, the number of people in the UK with dyslexia is estimated to be over 6 million, or 10% of the population. (Similar proportions of people with dyslexia are likely to be found amongst French speakers, but speakers of more orthographically transparent languages such as German or, especially, Italian are considerably less likely to be dyslexic with respect to those languages).

The number of colour-blind people in the UK is estimated to be around 3 million—about 1 in 12 men and around 1 in 200 women.


It should be clear from the relative sizes of these audience groups that if you are serious about accessibility you have to do more than just run a PDF though an automated checker.


The greater part of the solution to this problem requires that organisations train authors in how to create content that will be accessible to all. They also need to make sure that their brand guidelines are accessibility-friendly, particularly in terms of colour contrast, colour blindness and typography.

Manual evaluation of documents against a content-orientated standard such as WCAG is also essential, as is testing with multiple assistive technologies, not just screen readers.


Based on our more than 17 years’ experience in this field, our Accessible PDFs from InDesign and Accessible PDFs from Word training courses offer the most in-depth training available anywhere in both the technical and the content creation aspects of accessible PDF production, including, of course, how to test effectively.