Images in PDFs: Accessibility Best Practices

Why Image Accessibility Matters

Images in PDFs can significantly enhance your content, but if they are not used accessibly, they can create barriers for users with disabilities. Screen readers and assistive technologies rely on properly formatted images and alternative text (alt text) to convey meaning. Inaccessible images — including those containing text or used as the sole content of a PDF — can leave users without the critical information they need.

Addressing Image Accessibility in PDFs

Add Alternative Text for All Images

Alt text provides a concise description of an image’s purpose or content, allowing users with visual impairments to understand its meaning.

  • What to Include: Focus on the image’s purpose rather than its appearance. For example:
    • Informative image: “Event flyer for Digital Accessibility Workshop, January 15, 3 p.m., Moseley Center.”
    • Decorative image: Use an empty alt attribute (alt=””) to signal screen readers to ignore it.
  • How to Add Alt Text: Use tools like Adobe Acrobat Pro to apply alt text to images in your PDF.

Avoid Embedding Text in Images

Text within images cannot be read by screen readers, making the information inaccessible.

  • Examples to Avoid:
    • Event flyers designed in Canva or InDesign with all the event details embedded as part of the image.
    • Infographics with text-based data embedded directly in the graphic.
  • Solution: Always include text-based content in the PDF’s body, using proper tags and formatting. If you must include an image with text, duplicate the content in plain text elsewhere in the document.

Ensure Scanned Documents Are Searchable

Scanned documents often consist of images of text, making them inaccessible to assistive technologies.

  • How to Fix It: Use Optical Character Recognition (OCR) tools, such as Adobe Acrobat’s “Enhance Scans” feature, to convert scanned text into searchable, selectable text.
  • Important Note: Even after OCR, ensure the document has a logical reading order and proper tagging.

Verify Color Contrast in Images

Text or graphical elements within images must meet WCAG color contrast guidelines to ensure readability.

  • Examples to Avoid:
    • Light gray text on a white background.
    • Bright yellow text on a light background.
  • Solution: Test the contrast of text within images using tools like WebAIM Contrast Checker, and adjust colors as needed before embedding the image in your PDF.

Use Descriptive Captions Where Appropriate

For complex images, such as charts or graphs, a brief caption can provide additional context.

  • Example: “Figure 1: Enrollment trends at Elon University from 2015 to 2025.”
  • Pair the caption with detailed alt text or an accompanying description in the document body.

Common Mistakes to Avoid

  • Relying on Images for Critical Information: If the primary content of your PDF is an image (e.g., a scanned flyer or event announcement), users relying on screen readers will be unable to access the information. Always provide text-based alternatives.
  • Skipping Alt Text for Images: Images without alt text are inaccessible to users with visual impairments.
  • Using Low-Contrast Images: Poor contrast between text and background in images makes content unreadable for users with low vision or color blindness.
  • Failing to Apply OCR to Scanned Documents: Scanned text is unusable for assistive technologies until it is processed with OCR.

Final Tips for Image Accessibility in PDFs

  • Plan Accessibility from the Start: When designing content in tools like Microsoft Word, Canva or InDesign, ensure all text and critical details are included as plain text in the document.
  • Test Your PDFs: Use Adobe Acrobat’s accessibility tools to verify that images, alt text and other visual elements are properly formatted.
  • Avoid Overloading PDFs with Images: Excessive images can distract from your content and make navigation more difficult.
  • Include Alternative Formats: If your PDF contains complex images, provide a text-based alternative format for users who need it.

By addressing these image-related concerns, you ensure your PDFs are accessible, professional and inclusive, aligning with Elon University’s commitment to equity and accessibility.