PDFs, which stands for Portable Document Format, are files which encode an entire document into a digital format.
It is based around the principle of maintaining documents electronically much as they would be in their physical form.
The vast majority of PDFs are not accessible. This means that people with accessibility needs, like those who use a screen reader, or with a visual impairment, might not be able to use the document.
Common reasons that PDFs fail accessibility standards:
- a lack of structured data such as a hierarchy of headings, which means people who cannot see the pages cannot orient or navigate properly
- they cannot meet the range of users' accessibility needs, for example, users cannot change colours or font size - this is easy in web content, but much more difficult or impossible in PDF documents
- many browsers, tools and extensions do not work with them - they often have problems with zoom, scroll, audio, image and keyboard navigation
- a lack of 'alt text' for images - alt text provides an alternative way to convey the information provided by the image to users who cannot necessarily see the image
- they take users away from the website, opening in a new tab, window or software - and not all users have the right software
Some of these issues can be addressed, but others are much more difficult. This means that almost all PDFs are not accessible, and do not meet the legal standard required of public sector bodies.
This means that publishing information in a PDF format is likely to be unlawful, unless you also publish an accessible version.
Other problems with PDFs
Other reasons we avoid PDFs is because:
- they give people a poor user experience, especially on mobile
- they are hard to maintain and update, so users may get out of date and unreliable content
- if users find PDFs in search results, they get them without any supporting context or material
- search engines do not rank PDFs high in search results
- it's difficult to collect data on how people use PDFs, and that makes it difficult to identify problems and improve them