Portable Document Format (PDF) is a common file format that allows the layout of a document to look the same across different platforms and applications. This article explains how to view and create PDFs with accessibility in mind.
PDF files created by scanning a printed document will be inaccessible to screen readers because they are only an image of the page, not the text itself. You can tell if a file has been created using this method if the Select tool in Adobe Reader cannot be used to select text. If you have Optical Character Recognition (OCR) software you can convert the image into text, either from the PDF file or by printing it and re-scanning it into your OCR software; either method may require a lot of error correction. Another solution is to contact the source of the document and request an accessible version -- the source may be legally required to provide this.
Other accessibility problems occur in PDF documents. The two most common are the lack of a text description of any graphics, and a non-linear layout: columns, sidebars, and jump pages can confuse the order in which a screen reader tries to read the document.
Adobe Reader allows you to set up reading preferences via an Accessibility Setup Assistant, found in the Document menu. Use this together with any tools your screen reader has to make the reading experience better -- most screen readers have settings or scripts for Adobe Reader and other PDF reading programs.
You can also use some online and downloadable tools to convert the PDF file into HTML, likely to be more compatible with screen readers.
Adobe Reader and other PDF reading programs have good magnification and zooming features for use by people with low vision.
Creating Accessible PDFs
If you are using Adobe Acrobat to create your PDF, Adobe provides excellent guidance on accessibility. Many people create PDFs from their word processor or other programs, often as a "Print" option.
To create an accessible PDF, make sure that all graphics have a text equivalent and use your program's method of creating headings (not just manually chosen larger or bold font). Headings should be accurately 'nested' -- if Heading 1 is a title, use Heading 2 for a subtitle. Keep your layout as simple as possible so that the reading order will be obvious to screen readers.Once you have prepared the PDF, check it with Adobe Reader's Accessibility Quick Check in the Document menu, and make any necessary changes. Microsoft also has an Accessibility Checker built into the 2010 versions of Word, Excel, and PowerPoint.
Some screen reader users prefer an HTML or word processor version of a document, so you may want to make at least one of these available to your users. A best practice if you can only publish one version of a document is to publish it in HTML, which generally has the best screen reader compatibility and is widely accepted by non-disabled users as well.
Acrobat itself can be difficult to use to make files accessible, especially if accessibility is added retroactively. The PDF Accessibility Wizard (PAW) is an add-on for Microsoft Word 2007 that automates most of the processes for implementing accessibility.