Accessibility of PDFs
How to make PDFs more accessible.
PDFs can be bad for accessibility. It can be difficult for users to customise them for ease of reading, and often they do not work very well with assistive technologies like screen readers.
Wherever possible, create content in HTML formats. If you cannot avoid publishing a PDF, it should be in addition to an HTML version.
As a minimum, any PDF you publish must meet Level AA of the Web Content Accessibility Guidelines (WCAG) 2.0.
Making your PDF meet the WCAG standard
A PDF is only as accessible as the document it’s created from.
When a document is converted into a PDF, it’s tagged. The PDF tag tree reflects the structure of the document, and it’s this structure that assistive technologies like screen readers use to navigate the document.
It’s important to format your content properly to give it a logical structure, for example by using styles to create headings rather than just making them bold and increasing the font size.
Checking before publication
Once you’ve followed steps to make your document accessible, check your file before publishing.
Using Microsoft Office 2016
Use the accessibility checker found in the ‘Review’ toolbar.
In Adobe Acrobat Pro
Once you’ve converted your file to a PDF, you can check the accessibility of it (and other PDFs) in Acrobat Pro.
Go to ‘Advanced’ then ‘Accessibility’ and select ‘Full check’. The PDF should pass the full check for WCAG 2.0 Level AA without any warnings.
Quick screen reader check
Ask a screen reader user to read through the PDF. If no-one is available to do this, use one of the following options instead.
Non Visual Desktop Access (NVDA) is a free open source screen reader for Windows. It can be installed to the desktop or run from a portable USB thumb drive.
With NVDA running, open the PDF and use the following commands to check the PDF:
- from the top of the PDF (with the numlock off), use Numpad 0 + Numpad 2 to read the PDF from top to bottom and check the reading order
- use the tab key (repeatedly) to move through the PDF and check the tab order
- use the h key (repeatedly) to move through the PDF and check the heading structure
- use the g key (repeatedly) to move through the PDF and check for text descriptions
Please note, these commands will also work with the Jaws screen reader from Freedom Scientific.
All Apple Macs have VoiceOver built in. Turn VoiceOver on (or off again) using Command + f5. With VoiceOver running open the PDF and use the following commands to check the PDF:
- from the top of the PDF use a double finger down swipe, or ‘Control + Option + a’ to read the PDF from top to bottom and check the reading order
- use the tab key (repeatedly) to move through the PDF and check the tab order.
VoiceOver does not provide shortcut keys for navigating by headings or graphics.