PDF files, like other web content, must be ‘accessible’. This is now a requirement for all government publications, and strongly recommended for private sector publications.
For a PDF to be considered ‘accessible’ it must satisfy the requirements of the Web Content Accessibility Guidelines version 2.0 (WCAG 2.0), which considers:
- Use of colour for people with low vision, cognitive or colour perception impairment
- ‘Mouseless’ navigation for readers with mobility impairment or reduced fine motor control
- Communication of content and structure to people who are blind
PDF Techniques for WCAG 2.0 provides general guidance on how to create an accessible PDF.
While an existing PDF can be retrofitted for accessibility using a PDF editor like Adobe Acrobat Pro, it is far more efficient to build accessibility into the InDesign source file.
In this article you’ll learn key techniques for creating PDF files from InDesign that can be read by people who are blind.
- Instructions are provided for InDesign v6 or later (screenshots are from InDesign CC on a PC).
- A PDF Editor such as Adobe Acrobat Pro is needed to complete accessible PDF construction.
PDF tags are a basic requirement for accessible PDF files and are used by assistive technologies to read aloud PDF content or translate it into Braille.
Assistive technologies such as screen readers and Braille devices extract both content and structural composition from these tags. For example, they will convey whether content is a heading, subheading, list, link, image, form element or part of a data table.
There are tags for different content types, for example:
- <P>: paragraph
- <H1>-<H6>: Heading level 1 through to Heading level 6
- <Figure>: An image
- <Artefact>: Decorative content
- <Table>: A table with rows and columns
InDesign tagging tools
Set up your InDesign file to include tags in PDF exports.
Tagged headings communicate their content and structure to readers who are blind. These heading tags can be scanned by readers as they navigate their way through document content.
Tag all headings by assigning and configuring paragraph styles.
- Type > Paragraph Styles > Export tagging
- Choose the tag that represents your heading’s logical nesting in the document structure. In the following example our nested heading is assigned ‘H2’.
Paragraph text and lists
The good news is you do not need to separately tag paragraph text or lists. Paragraph text will automatically be tagged as <P>. Lists will automatically be tagged as <L>.
Data table tags help people who cannot see the table to understand the relationships between table headers and table data.
Sighted readers intuitively relate data to headers to understand its meaning. For example, it is easy to see from the following table that Leona consumed 38 grams of chocolate. Tagging provides context for how the data should be read for those who can’t see it.
|Consultant||Coffees consumed (ml)||Chocolate consumed (g)|
To recreate this simple table in a tagged PDF we can add rows of column headers with InDesign:
- Create a new table with one row of headers: Table > Insert Table
- Specify the number of header rows. Cells in these rows will be tagged as <TH> (Table Header)
Note: InDesign will not allow you to assign columns of row headers. You’ll need to add these after export using your PDF Editor (such as Adobe Acrobat Pro).
Images are also tagged as <Figure> elements by default. Alternative (‘alt’) text should be provided for informative images as a substitute for people who can’t see them.
- Object > Object Export properties
- Alt Text tab > Alt text source: Custom (add ‘alt’ text)
- Tagged PDF tab:
- Apply tag: Based on Object
- Actual text source: Custom
PDF files commonly contain images that add designer flair but do not communicate additional information to accompanying text. These decorative images should be hidden from screen readers.
- Object > Object Export properties
- Tagged PDF tab > Apply tag: Artefact
Anchor images into the text flow
Make sure your images are read precisely where you want them to be read, by anchoring them into the text flow:
- Add image: File > Place
- Anchor your image: Drag the ‘blue square’ in the image border to its place in the text. Once anchored the ‘blue square’ becomes an ‘anchor’.
Apply the following settings to ensure your tags are retained in the PDF after export.
- File > Export (choose Adobe PDF (Interactive) file type)
- Name your file
- Export to Interactive PDF settings:
- View after exporting
- Embed page thumbnails
- Created Tagged PDF (checked)
- Use structure for Tab Order (checked)
There are a few further steps you’ll need to complete with your PDF editor to optimise your PDF export for people who are blind, such as correcting table row header tags, and setting the document title and language. However, these are the key steps required to create a tagged PDF export that is accessible to people who are blind.
Learn InDesign accessibility skills
To be fully accessible there is so much more you can do with InDesign before PDF export, such as optimising your use of colour, stacking tags in correct reading and tabbing sequence, adding file metadata, table of contents and bookmarks, and perhaps labelled form fields.
Contact us to find out more about our Accessible PDF from InDesign consultancy option, which gives design teams the chance to work directly with one of our accessibility experts to learn:
- The principles of accessible document design
- How to apply accessible document design principles using Adobe InDesign
- How to incorporate accessibility into existing document creation processes
- How to optimise PDF output with Adobe Acrobat Pro to achieve WCAG 2.0 Level AA compliance
Contact Digital Access for more information.