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Why the Acrobat Accessibility Checker doesn't guarantee accessibility in PDFs

Updated: Mar 16, 2023


screenshot of Adobe Acrobat tags panel and the checker box

This year marks 10 years since I started my accessibility journey, and hindsight has taught me many things in that time. One such thing I'm kicking myself about is how I used to remediate a document back when I started. Granted, I was going off the information I had at the time, and it was a case of doing my best. But hindsight is a wonderful thing.


Like most people new to the PDF accessibility world, I initially thought that once a PDF passes the inbuilt Adobe Acrobat accessibility checker, it's accessible and usable.

Well, not exactly.

Sure, Adobe Acrobat Checker is a great starting point that checks for some basic accessibility requirements. But there are a great many things the checker can't catch.

What the Acrobat checker does right


The checker does look for a significant number of accessibility considerations in a document. Here's a list of just a few areas it covers;

  • if it is a tagged PDF

  • if text alternatives for images (alt text) are present

  • that no heading levels are skipped in the heading hierarchy

  • if lists have been created properly

  • if there are header rows in a table

That sounds like a good start...

What the Acrobat checker misses


However, let's look at the mentioned topics from another angle. Let's explore what the checker does miss.

  • Tagged PDF - the checker cannot identify if elements have been tagged correctly, i.e. a heading may be tagged as a paragraph and would be read as such.

  • Alt text - It can't recognise if alt text is suitable, i.e. incorrect, too long or, at worst, automatically generated - that rarely produces good results.

  • Heading levels - in instances where headings have been tagged incorrectly, i.e. a heading level 5 (H5) should be tagged as an H4, yet the checker is blissfully unaware.

  • Lists - The checker would ignore lists tagged incorrectly as paragraphs. (Note to InDesign users, ensure your List styles are tagged as Automatic; trust me on this one).

  • Table header rows - While the header rows are passed, the checker can't identify if the rest of the table is set up correctly, which is especially problematic in more complex tables.

There are several other considerations that the checker cannot evaluate, including colour contrast, correct tag order for screen reader users and reading order for reflow users, to name a few.

The solution?


In short, the best method is to set up the native file correctly and carefully review the exported PDF using various methods. The best place to start is in Adobe Acrobat Pro to ensure everything is appropriately marked so that all users can read the document the same way it was designed to be read, and yes, doing a first check using the built-in in checker.

After this, I always look to the PDF Accessibility Checker 2021 (PAC 2021) for a more comprehensive check. PAC 2021 is an excellent tool for reviewing and advising errors according to WCAG standards and ensuring a more usable file. I then listen to the PDF with a screen reader such as NVDA and pick up any mistakes which may not be apparent.

Moving forward


No matter where you are in your accessibility journey, there is always something to learn. I wish I had known then of the limitations of the Adobe Acrobat checker, but when we know better, we do better. (And now you know, in case you didn't already!).

Hence my process has changed significantly, and the checker is only used as a starting point. As we know, there is so much more that goes into making an accessible and usable PDF; and other remediation tools, attention to detail and review by a screen reader are vital.

So next time someone tells you their PDF is accessible because it passed the Acrobat checker, it is worth discussing whether further checks may be needed.

And if they need clarification on the process, or you would like to know more, help is always available. There's nothing worse than spending hours finding a solution to a problem when it could have been solved by speaking to someone. (Speaking from experience on that one...)

Let's make the world more accessible, even if it's one PDF at a time!


Drop me a line at KC & the Graphics Bandwagon if this resonates, and remember, help is only a call or a click away.

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