Adobe made significant improvements to accessibility with the release of InDesign CS5.5. The following are some basic steps for creating accessible documents in InDesign. These steps apply specifically to InDesign CS5.5, which includes significant improvements to accessibility support over previous versions. For comparison sake, each steps includes a note regarding how to attain a similar level of accessibility using CS4.

For information that applies to later versions, plus a variety of other instructional resources, see the Adobe InDesign Accessibility site.

Tips for Optimizing Accessibility in CS5.5

Create your document using paragraph styles (Window > Styles > Paragraph Styles). These aren’t just a good idea—they’re required for accessibility. Use them consistently throughout the document to define styles for all text, including headings and sub-headings. For headings, use styles that indicate the heading level (e.g., Heading1, Heading2) within the organizational structure of the document (headings should form an outline of the document).
Associate each of the styles you’ve created with specific PDF tags. From the Paragraph Styles options menu, select Edit All Export Tags, check the PDF radio button, then select the relevant tags for each of your styles.
Add alt text to images (Object > Object Export Options > Alt Text).
Establish content read order with the Articles panel (Window > Articles). Simply drag content from the document into the Articles panel in the order in which it should be read by screen readers. To drag multiple items, select them in the correct read order using Shift+click, then drag them all at once to the Articles panel.
Export to PDF, and be sure to select “Acrobat 6” or higher for Compatibility, and check the “Create Tagged PDF” checkbox.