The importance of PDF accessibility
PDFs are by far the most common document format found in websites. They can be created by converting or exporting many different digital file types, as well as by scanning or digitizing existing paper documents. PDF files often need to function both digitally and printed out; for example, we can make accessible forms, which can be filled on the computer and then printed to be submitted as hard copies.
Most PDFs can be made accessible by following a few steps, which will sound familiar if you have ever created accessible HTML documents. All PDF documents must be tested before publishing, regardless of what authoring tool was used to create them, in order to make sure they meet the appropriate accessibility standards. You can learn how to do this on our testing document accessibility page.
Exporting tagged PDFs
Many authoring tools can create a tagged PDFs, by adding markup tags to describe the document structure and attributes, including its language, headings, lists, tables, and image content with text alternatives. PDF tags are similar to HTML tags, but not identical; for example, the
<Figure> tag is used to describe an image, just like the
<img> tag in HTML.
In Microsoft Office suite
The process for creating tagged PDFs from Microsoft Office documents varies slightly between operating systems, programs, and versions; but they all involve the following general steps:
- Run the Accessibility Checker tool to locate any possible accessibility issues.
- Fix issues if necessary.
- Export using the “tagged PDF” option.
In Adobe InDesign
- Create separate Paragraph Styles for all types of text: headings, actual paragraphs, etc. Name them accordingly.
- Map each Paragraph Style to the corresponding PDF tag by going to: Window > Type & Tables > Paragraph Styles > Export Tagging.
- Add text alternatives to image content by selecting the image and going to Object > Object Export Options > Alt Text.
- Define the content reading order by going to Window > Articles.
- Export as Adobe 6 or higher and check the “tagged PDF” option.
Tagging existing PDFs
Some document authoring tools (such as Google Docs or Google Slides) do not currently offer the option of exporting tagged PDFs. You can add tags to existing PDFs with the help of Acrobat Pro and similar tools, such as PhantomPDF by Foxit.
Tagging PDFs in Acrobat Pro
You can use Adobe Accessibility Tools to add tags to the different types of content on a PDF, including:
- A table of contents with links to the correct pages
- Headers and footers
- Tables (including column and row headings)
- Forms and form fields
- Image content with text alternatives
- Decorative images hidden from assistive technologies
Some security settings can prevent assistive technologies from accessing a PDF document and can also prevent the ability to check and fix accessibility issues after exporting, if possible, export PDFs without security settings. If security restrictions are required, learn how to set PDF security that permits accessibility.
Adobe Accessibility Tools also allow you to check and fix reading order, tab order, document language, and colour contrast issues, amongst others. This process is similar to the steps described in our testing document accessibility page.
Scanning paper documents
When a paper document is digitised using, for example, a dedicated scanning device or a scanning app in a smartphone, the resulting digital file will be an image, even if it’s saved as a PDF.
The first step in making these scanned documents accessible is to transform the image into actual text, using OCR (Optical Character Recognition) software. Some scanning devices and applications come with built-in OCR, and standalone OCR programs are also available. The resulting text can be saved, for example, as a Word or PDF document, although it’s often necessary to manually check that the text output is correct.
The second step would be to transform the output text into a tagged PDF document, using the processes described earlier in this page.
- Techniques for WCAG 2.1: PDF on the W3C website
- PDF accessibility overview by Adobe
- PDF Accessibility by WebAIM
Creating accessible PDFs:
- Create accessible PDFs from Microsoft Office programs by Microsoft
- Make a PDF document accessible from Adobe InDesign and Acrobat Pro by PDF Accessible
- Create and verify PDF accessibility (Acrobat Pro) by Adobe
- Creating Accessible PDF forms using Acrobat Pro by the University of Washington
Improving the accessibility of existing PDFs: