Why are accessible pdfs so much trouble?
- Pdfs were developed in the late 1990s as an export option, just like a printer or image file.
- Most times they were scanned paper documents that were saved as image files.
- They were never intended to have an editing environment.
- When they were introduced, the use of assistive technology to read pdfs was not available.
PDF UA is the ISO standard for accessible pdfs. Example items in it are:
- Clear rules for developers and authors of tagged pdf documents and forms.
- Tags must correctly represent documents’ semantic structures (headings, etc.).
- Graphics have alt text.
- Security settings must allow assistive tech to access content.
- Fonts must be embedded, and text must be mapped to Unicode (normally happens automatically).
Pdfs are very common, so it’s helpful to know if one is functionally accessible and technically accessible.
Accessibility checkers give you an overview about whether a pdf is technically accessible, but passing the accessibility checker might not mean it is functionally accessible.
Structure of an Accessible Pdf
- What we see when we look at the pdf.
- This is sometimes called the hard copy layer/physical layer.
Text Layer (Invisible)
- Needed for accessibility.
- Contains all the text.
- Enables searching and editing in the document.
- If you turn on read aloud, this is what is read.
- Reads top to bottom, left to right with no formatting.
Tags Layer (Invisible)
- Needed for accessibility.
- Enables the pdf to be accessible because it gives the document semantic structure.
- Where you assign text tags like headings, paragraphs, etc.
- Gives the text meaning.
Quick Accessibility Checks
Scanned Document Tests
Open the pdf and run the accessibility checker.
Or do the following quick checks:
- Open it up and if it says it is a scanned document it is not accessible.
- Might need to go to the original document and export.
Text vs. Image Tests
- Place the cursor in a text area of the document. If the i-bar shows up (instead of the + sign) you know it is text and not an image.
- If you can highlight some text, then it is text and not an object/image.
- Open the Tags panel. If it states there are no tags available, then the pdf is not accessible.
- Acrobat may have tried to give it tags (say, paragraphs) but they might not make sense or be appropriate.
- If there are tags, are they correct? Are they in the correct order (ex.: is the semantic order of headings correct or out of order?) and do items look correctly mapped?
Alt Text Quick Test
- Open the Reading Order dialog box and look at items tagged as “Figures” (nontext elements like images).
- If there is no alt text, then it is not accessible.
- If alt text is present, make sure it makes sense for the figure.
Verify Reading Order
- If it is a straight top-to-bottom document, then you might not need this step.
- In the Tags panel, select the first tag in the tree and then use the down arrow to move through the tags to ensure that they follow logically with the text and are in the correct order.
Tagging the document will often be enough.
- Make sure all checking options are selected.
- You don’t have to create a report but you might want to if, for example, you need to provide it to another person.
- Logical reading order and color contrast need manual checks.
- It is quite good at finding issues.
Correcting Tag Issues
- Do not use the Fix option.
- Open the Reading Order pane:
- Clear tags.
- Highlight the element you want to tag and then in the Reading Order pane indicate what type of element it is (ex.: heading 1).
- Continue down the page highlighting items.
- For tables, define the element as a table first and then go into the table editor.
If a document with lots of images was created in InDesign, the best solution is to go to the original document and make it accessible in InDesign instead of modifying the pdf.
- Watch a tutorial on making an InDesign document accessible.
- Make sure you export to pdf instead of printing to pdf.
- Make sure each slide title is unique (will become headings).
- Use the accessibility checker.
- Stick to using the standard layouts since they are designed to use correct reading order.