Checkpoint 28: Annotations

Links, form fields, comments, and other interactive elements (annotations) must be properly tagged, have alternative descriptions, and follow correct reading order so all users can access and interact with them.

What This Means

PDF annotations include interactive elements like:

• Links: Clickable text or images that navigate to URLs or other locations
• Form fields: Text inputs, checkboxes, radio buttons, dropdowns
• Comments and notes: Sticky notes, text annotations, highlights
• Media elements: Embedded video or audio
• File attachments: Documents attached to the PDF

For these elements to be accessible:

1. They must be tagged with appropriate structure tags (Link, Form, Annot)
2. They must have alternative descriptions for screen readers
3. They must be in logical reading order for keyboard navigation
4. They must have proper tab order for form completion

Why It Matters

Annotations provide functionality beyond static reading. When they are inaccessible:

• Links become invisible to screen reader users who cannot see or click them
• Forms are impossible to complete without proper field labels and structure
• Tab order confusion makes keyboard navigation unpredictable
• Missing descriptions leave users guessing about link destinations or field purposes
• Media content becomes inaccessible without alternatives

Interactive PDFs are increasingly common for applications, contracts, and web content. Making annotations accessible ensures all users can complete tasks and access information.

Common Violations

The Matterhorn Protocol defines eighteen failure conditions for annotations. Here are the most common ones grouped by category.

Link Issues

28-011: Link Annotation Not Nested Within Link Tag (Machine Testable)

What's Wrong: A clickable link exists in the PDF, but it is not properly nested inside a Link structure tag. Screen readers cannot identify it as a link.

How to Identify:

• PDF/UA validators will flag this error
• Check the Tags panel for Link tags containing link annotations
• Test with a screen reader to see if links are announced

How to Fix:

1. In the Tags panel, create a Link tag if one does not exist
2. Locate the link annotation in the Content panel
3. Associate the annotation with the Link tag:
   • Use the Reading Order tool to restructure
   • Or manually drag the annotation reference under the Link tag

28-012: Link Annotation Missing Alternate Description (Machine Testable)

What's Wrong: A link does not have alternative text in its Contents key. Screen readers cannot describe the link destination.

How to Identify:

• PDF/UA validators will report this
• Check link properties for Contents or alternate text fields

How to Fix in Adobe Acrobat:

1. Go to Tools > Edit PDF
2. Click on the link
3. Right-click and select Properties
4. In the General tab, add a description in the Description field
5. Click Close

Or through the Tags panel:

1. Find the Link tag
2. Right-click > Properties
3. Add Alternate Text that describes where the link goes

Form Field Issues

28-005: Form Field Missing Alternative Description (Machine Testable)

What's Wrong: A form field does not have a tooltip or alternative description. Screen reader users will not know what information to enter.

How to Identify:

• PDF/UA validators flag fields without tooltips
• Test the form with a screen reader
• Check form field properties for empty Tooltip field

How to Fix in Adobe Acrobat:

1. Go to Tools > Prepare Form
2. Click on the form field
3. In the properties panel on the right, find Tooltip
4. Enter a clear description: "Enter your first name" or "Select your country"
5. Repeat for all form fields

28-010: Widget Annotation Not Nested Within Form Tag (Machine Testable)

What's Wrong: A form field widget exists but is not properly nested within a Form structure tag.

How to Fix:

1. In the Tags panel, create a Form tag
2. Move the form field's widget annotation under the Form tag
3. Ensure the tag structure properly represents the form

Reading Order Issues

28-001: Annotation Not in Correct Reading Order (Human Testing)

What's Wrong: Annotations (links, form fields) are not in a logical reading order. When users tab through the document, the focus jumps unpredictably.

How to Identify:

• Tab through the document and note the order
• Check if focus moves logically from top to bottom, left to right
• Test with a screen reader navigating through links

How to Fix:

1. Open the Tags panel
2. Expand to show annotation locations
3. Drag and reorder tags to match visual/logical order
4. Test by tabbing through the document

28-008: Page Containing Annotation Missing Tabs Key (Machine Testable)

What's Wrong: A page with annotations does not have a Tabs entry specifying how to handle tab order.

How to Fix: This requires low-level PDF editing. In Acrobat:

1. The fix is usually to set the Tabs key to "S" (structure order)
2. Use Preflight with a fixup that adds the Tabs key

28-009: Tabs Key Value Other Than S (Machine Testable)

What's Wrong: The page's Tabs key is set to something other than "S" (structure order). Tab order may not follow the tag structure.

How to Fix:

1. Use Preflight to create a fixup
2. Set the Tabs entry to "S" for structure order
3. Verify by tabbing through the page

Annotation Tagging Issues

28-002: Annotation Not Nested Within Annot Tag (Machine Testable)

What's Wrong: A generic annotation (comment, note) is not properly contained within an Annot structure tag.

How to Fix:

1. In the Tags panel, create an Annot tag
2. Move the annotation reference under the Annot tag
3. Verify with a PDF/UA validator

28-004: Annotation Missing Alternative Description (Machine Testable)

What's Wrong: An annotation lacks descriptive text in its Contents entry.

How to Fix:

1. Select the annotation in the document
2. Right-click and choose Properties
3. Add descriptive text to the Description or Contents field

Media and Attachment Issues

28-014: CT Key Missing from Media Clip Data Dictionary (Machine Testable)

What's Wrong: Embedded media (audio/video) is missing the content type specification.

How to Fix: This requires low-level PDF editing to add the CT (content type) entry to media objects. Consider re-embedding media using tools that create compliant entries.

28-015: Alt Key Missing from Media Clip Data Dictionary (Machine Testable)

What's Wrong: Embedded media lacks an alternative text description.

How to Fix:

1. Locate the media object in the document
2. Add alternative text describing the media content
3. For video: describe visual content
4. For audio: provide transcript reference

28-016: File Attachment Annotations Do Not Conform to 7.11 (Machine Testable)

What's Wrong: Attached files do not meet PDF/UA requirements for file attachments.

How to Fix:

1. Ensure attached files are also accessible (if they are PDFs)
2. Provide descriptions for all attachments
3. Consider whether attachments are necessary

Special Annotation Issues

28-017 & 28-018: PrinterMark Annotation Issues (Machine Testable)

What's Wrong: Printer marks (crop marks, registration marks) are either included in the logical structure or not marked as artifacts.

How to Fix:

1. Printer marks should never be in the tag structure
2. Remove printer marks from the Tags panel
3. Mark printer mark appearance streams as artifacts
4. Consider removing printer marks from accessible documents

How to Fix in Adobe Acrobat

Editing Link Properties

1. Go to Tools > Edit PDF
2. Click on the link (links are highlighted)
3. Right-click and select Properties
4. Actions tab: Verify the link action is correct
5. General tab: Add a description
6. Appearance tab: Ensure the link is visible to sighted users

Creating Accessible Forms

1. Go to Tools > Prepare Form
2. For each field:
   • Click to select
   • In the right panel, add a Tooltip (this becomes the accessible name)
   • Set appropriate field type (text, checkbox, dropdown, etc.)
3. Test tab order:
   • Go to Tools > Prepare Form > More > Set Tab Order
   • Choose "Order Tabs by Row" or manually set order
4. Run Accessibility Checker to verify

Setting Tab Order

1. Go to Tools > Prepare Form
2. Click More in the toolbar
3. Select Set Tab Order
4. Choose ordering method:
   • By Row: Left to right, top to bottom
   • By Column: Top to bottom, left to right
   • Document Structure: Follows tag order
5. Or manually number fields

Fixing Reading Order for Annotations

1. Go to Tools > Accessibility > Reading Order
2. Review the numbered regions
3. Annotations should be in logical positions
4. Adjust as needed by:
   • Drawing new regions
   • Using the Tags panel to reorder

Adding Annotation Alt Text via Tags

1. Open the Tags panel
2. Find the Link, Annot, or Form tag
3. Right-click and select Properties
4. Go to the Tag tab
5. Enter Alternate Text
6. Click Close

How to Fix in Microsoft Word

Creating accessible interactive elements in Word helps produce better PDFs.

Creating Accessible Hyperlinks

1. Select the text to become a link
2. Press Ctrl+K (or Cmd+K) to insert hyperlink
3. Enter the URL
4. Ensure the link text is descriptive:
   • Good: "Download the annual report"
   • Bad: "Click here" or raw URLs
5. Click OK

Creating Accessible Forms in Word

Word forms have limited accessibility. For complex forms:

1. Use Content Controls from the Developer tab
2. Add titles and tags to each control
3. Consider creating forms in Adobe Acrobat instead for better control

Export Considerations

When saving as PDF:

1. Ensure Document structure tags for accessibility is checked
2. Links created in Word generally transfer well
3. Form fields may need additional work in Acrobat

Testing Your Fix

Automated Testing

Adobe Acrobat:

1. Go to Tools > Accessibility > Accessibility Check
2. Run the full check
3. Review:
   • "Alternate text" for annotations
   • "Links" section for link issues
   • "Forms" section for form field issues
   • "Tab Order" verification

PAC (PDF Accessibility Checker):

1. Open the PDF in PAC
2. Run the PDF/UA check
3. Review Checkpoint 28 results
4. Check all 18 failure conditions

Keyboard Navigation Test

1. Open the PDF
2. Press Tab repeatedly
3. Verify:
   • Focus moves in logical order
   • All interactive elements are reachable
   • Focus is visible (you can see where you are)
   • You can activate links with Enter
   • Form fields are accessible

Screen Reader Testing

1. Open the PDF with a screen reader
2. Navigate through links:
   • Press K or link navigation key
   • Verify link destinations are announced
3. Navigate through form fields:
   • Press F or form field key
   • Verify field labels are announced
4. Test form completion:
   • Can you fill out fields?
   • Are error messages accessible?

Link Purpose Test

1. Navigate to each link with a screen reader
2. Without seeing the page, can you tell where each link goes?
3. Is the link text meaningful out of context?

Validation Checklist

• All links are nested within Link tags
• All links have alternative descriptions
• Link text describes the destination
• Form fields have tooltips/labels
• Form fields are in Form tags
• Tab order is logical
• Tabs key is set to "S" on pages with annotations
• Media has content type and alt text
• File attachments are described
• Printer marks are artifacts (not tagged)
• Annotations are in correct reading order

Additional Resources

Official Standards and Guidelines

• W3C WCAG 2.1 Success Criterion 1.1.1: Non-text Content
• W3C WCAG 2.1 Success Criterion 2.4.3: Focus Order
• W3C WCAG 2.1 Success Criterion 2.4.4: Link Purpose (In Context)
• PDF Association Matterhorn Protocol 1.02

Tutorials and Guides

• Adobe: Creating Accessible Forms in Acrobat
• WebAIM: Creating Accessible Forms
• WebAIM: Links and Hypertext

Tools

• PAC (PDF Accessibility Checker) - Free PDF/UA validation
• NVDA Screen Reader - Free screen reader for testing
• Adobe Acrobat Prepare Form Tool

This documentation is based on the Matterhorn Protocol 1.02, the definitive reference for PDF/UA validation. For the most current information, consult the PDF Association and W3C WCAG guidelines.