Rationale
Portable Document Format (PDF) documents are used for information intended for download. To read these documents browsers must have the Adobe Acrobat plugin installed. Not all browsers, for example text-based browsers, can support this plugin however. In addition to this screen readers and braille output struggle to read this format.
Adobe has done a lot of work toward making PDFs as accessible as possible. Acrobat 7 Professional and Standard have full tagging tools and an accessibility checker to enable the production of accessible tagged PDFs.
Techniques
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Alternative formats should be provided for PDF content where possible. If you offer a PDF file, consider having the same content presented in HTML, Word or text format.
We strongly recommend that PDF forms have an alternative format provided, as they are particularly difficult to make accessible. Often forms are presented in PDFs as they are intended to be filled in offline, as they need a signature. Even when this is the case enabling the form to be filled in online is a huge benefit to many users.
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Create accessible PDFs using Acrobat's built in accessibility tools and checker. Ensure the PDF document has structure, correctly captioned images, and navigable content. Links to Adobe help and support can be found in the further information section below.
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Access Adobe help should be provided on every page that has PDFs, including links to Access Adobe and the PDF to HTML conversion tool. Additional help should also be given in a Help page elsewhere on the site. PDF help can be found in the RNIB help page.
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PDF link text should be intuitive and informative. Include information on the document contents, file format and size, so that users know exactly what they will get and how long it will take to download.
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New window warnings must be provided if PDFs open in a new window. This can either be in a piece of text at the top of the page, if there are a lot of PDFs; within the link text; in the ALT text if an image forms part of the link; or in text immediately preceding the link.
Testing tips
Verify that, as a minimum, each page with a PDF has a link to the Adobe conversion tool. Check for HTML, Text or Word alternatives and ensure the PDFs have been created with accessibility in mind. Check also for new window warnings and clear link text.
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Accessibility toolbar - Go to Doc Info - List Downloadable Files [new window]. Lists all links on the page to non-HTML documents by file extension (.ZIP, .PDF, .DOC. etc).
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Browser - Manually check pages to ensure there are alternative formats (where possible), links to Access Adobe and clear link text to documents.
Open PDFs and test their accessibility by running them through the Adobe Acrobat PDF to HTML conversion tool. If they have been structured badly and images have not been given captions the HTML output will be difficult to understand.
Further information
Compliance with WCAG 1.0
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11.4 If, after best efforts, you cannot create an accessible page, provide a link to an alternative page that uses W3C technologies, is accessible, has equivalent information (or functionality), and is updated as often as the inaccessible (original) page. Priority 1
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11.1 Use W3C technologies when they are available and appropriate for a task and use the latest versions when supported. Priority 2
For more information on techniques visit the Web Accessibility Initiative techniques page.