PDF (Portable Document Format) is a popular and commonly-used format for the delivery of visually formatted documents, typically intended for printing.
PDF documents may be created in one of several ways, and may contain text, images, and other kinds of common document objects. Depending on the content and construction of a PDF, it may pose significant accessibility barriers to some users, including users of assistive technology.
Potential PDF Accessibility Barriers
A scanned PDF contains no tags, structure, or other information to provide content or context to AT users. The scanned PDF presents a major accessibility barrier, and should not be distributed without significant remediation.
Untagged PDFs include content that is exposed to assistive technology, but that lacks structure, semantics, or order. Untagged PDFs must be tagged and checked for content order before distribution.
PDF with Images
PDFs may contain images that are intended to convey important information to users. These images must be accompanied by a text alternative, so that users are able to determine the purpose or function of the image.
PDF with Tables
PDFs may contain tables that are intended to convey important tabular data to users. If the table does not convey the relationship of header and data cells, or if the table is very complex, users may be unable to determine the context of a given cell or data point.
PDF lacking a Page Title
PDFs should contain a Page Title in the Document Properties, which is exposed to assistive technology when the document is opened. This information assists the user to understand the purpose of the document. If the Page Title is missing or not exposed to the AT, the user may not understand the purpose of the document.
PDF with Forms
PDFs are often used to deliver forms for print or online completion. Form elements must be appropriately labeled to convey their purpose to assistive technology. If form elements are unlabeled or improperly labeled, users may be unable to determine the purpose of the form elements.
PDF with Embedded Multimedia
Embedded multimedia is likely to lack captions, keyboard operable players, and screen reader support. Multimedia embedded in PDF should be avoided altogether.