1. Document Structure

A properly structured document provides navigation landmarks and helps users understand the organization and flow of information.

Best practices:

• Use heading styles (H1, H2, H3) in a logical hierarchy
• Create a table of contents for longer documents
• Use paragraph styles consistently
• Include bookmarks for navigation in longer documents
• Set the document language in the PDF properties

2. Alternative Text for Images

Alternative text (alt text) provides a textual description of images for users who cannot see them.

Best practices:

• Provide concise, descriptive alt text for all informative images
• Make alt text functional (describe what the image does, not just what it shows)
• Mark decorative images as "artifacts" or provide empty alt text
• Describe complex charts or graphs thoroughly, including key data points

3. Text Properties

Text should be selectable, searchable, and properly formatted to be accessible.

Best practices:

• Ensure all text is actual text, not images of text
• Use fonts that are clear and readable (sans-serif fonts are often best)
• Set text size to a minimum of 12 points for body text
• Avoid justified text alignment (use left-aligned text)
• Provide sufficient spacing between lines and paragraphs

4. Color and Contrast

Color should not be the only method of conveying information, and there should be sufficient contrast between text and background.

Best practices:

• Maintain a contrast ratio of at least 4.5:1 for normal text
• Use patterns, labels, or other indicators in addition to color
• Avoid color combinations that are problematic for people with color blindness
• Test your document with color blindness simulators

5. Tables

Tables should be properly structured with headers and appropriate markup.

Best practices:

• Specify header rows and columns
• Keep tables simple and avoid merged or split cells if possible
• Provide a caption or summary of the table content
• Don't use tables for layout purposes

6. Links

Links should be clearly identifiable and have descriptive text.

Best practices:

• Use descriptive link text instead of "click here" or URLs
• Ensure links are visually distinct from surrounding text
• Maintain consistency in link styling throughout the document
• Consider adding link destinations in parentheses for printed versions

7. Forms

If your PDF contains forms, they must be properly tagged and include clear instructions.

Best practices:

• Label all form fields clearly
• Provide instructions for completing the form
• Include tooltips for form fields
• Set a logical tab order
• Ensure form field validation messages are accessible

Built-in Accessibility Checkers

Adobe Acrobat Pro includes an accessibility checker that can identify many potential issues. Other PDF editing tools may have similar features.

Screen Reader Testing

Test your document with a screen reader like NVDA (free), JAWS, or VoiceOver to ensure it reads content correctly and in a logical order.

Keyboard Navigation

Try navigating your document using only a keyboard to ensure all content is accessible without a mouse.

Color Contrast Analyzers

Use color contrast analyzer tools to ensure your text meets accessibility standards for contrast ratio.

Balancing Accessibility and File Size

For the best balance between accessibility and file size:

• Start with a well-structured, accessible document
• Optimize images before adding them to your PDF
• Choose an appropriate compression level based on your needs
• Test the compressed document for accessibility issues