PDF accessibility principles
The Portable Document Format (PDF) is not considered an “accessible technology” by the Australian Human Rights Commission (AHRC) as it cannot provide an equivalent experience for a person with a disability to that of a person without a disability. As a result, the AHRC recommends the incorporation of accessibility features in PDFs to improve accessibility for some PDF users, and that an accessible alternative is also provided.
Document accessibility is important to people with the following disabilities:
- Low vision
- Motor impairments
- Cognitive impairments
AGIMO PDF study
In 2010 the Portable Document Format (PDF) Accessibility Review Project was carried out by the Australian Government Information Management Office. This study was designed to improve awareness of PDF accessibility capabilities by testing PDFs against the technology-neutral Web Content Accessibility Guidelines 2.0 (WCAG2). A variety of PDFs were tested, including:
- Adobe tagged “best practice” PDFs
- Specialist tagged PDFs; and
- Non-tagged PDFs
The study revealed that while the PDF specification allows for the inclusion of a variety of features that can improve access for people with a disability, other issues also contribute to the inaccessibility of PDF files.
The issues that result in an inaccessible PDF file are, in order of impact:
- the design of the PDF file to maximise accessibility the document author needs to incorporate document structure, tags and elements
- the technical ability of the assistive technology interaction between assistive technologies such as screen readers and the PDF.
- the skill of the user using an assistive technology with a PDF requires a different skill set to using HTML.
Accessibility needs to be considered both when creating a PDF and when publishing a PDF on the internet.
Requirements for PDF accessibility include, but are not limited to:
- PDFs should always have an accessible alternative, such as HTML, Word, Text or RTF
- PDFs must be tagged with accessibility features, such as:
- Headings and text
- Alternative text for images
- Tables and lists;
- Bookmarks; and
- PDF forms must be coded with accessibility techniques
- Page numbers must be specified for consistency across PDF readers
- The document title and language must be specified
- Bookmarks must be used in addition to headings to navigate content; and
- All text must be searchable (i.e. the PDF is not a scanned image)
Requirements for HTML accessibility include, but are not limited to:
- PDF must be published with an equivalent accessible alternative (HTML, Word, Text or RTF);
- The link to the alternative version must be placed adjacent to the PDF link;
- PDF (and its alternative) link text must:
- be purposeful, descriptive and meaningful;
- indicate the target is a PDF;
- not use ASCII characters, ambiguous words (e.g. ‘more’, ‘here’), or device-dependent words (e.g. ‘click’); and
- be consistently presented for all downloads.