content-tag-invalid

Ensure meaningful content in PDFs is properly tagged, with relevant attributes, and mark non-meaningful content as artifacts.

Description

All meaningful content in PDFs need to be properly tagged with relevant attributes. Similarly, decorative and non-meaningful content should be marked as artifacts.

Such clear tagging helps assistive technologies like screen readers to identify elements accurately.

You can follow these guidelines to comply with this rule:

1. Real content must be in proper tags

   • Every piece of real content (text, images, tables, etc.) must be placed inside a meaningful structure element (tag).
   • These tags help define what the content is (e.g., a paragraph, table, figure).
   • The definitions of these tags come from the PDF standard (ISO 32000-2:2020).
2. Some tags are just for grouping, not meaning
   • Some structure elements, like Div and Span, don’t have specific meanings by themselves.
   • Div groups multiple elements together.
   • Span is used to apply formatting (like bold or italic) to specific text.
3. Attributes must match the context
   • Some attributes (extra details added to tags) are useful only in certain situations.
   • For example, the Placement attribute helps position images:
   • If an image is inside a paragraph, it should have an inline placement.
4. Content should be tagged logically, not based on layout
   • The document’s meaning should be preserved even if it’s split across pages or columns.
   • Example: A long paragraph that flows across two pages should still be in a single P (paragraph) tag, not split into two separate paragraph tags.
5. Tables and other elements should stay together
   • A table that spans multiple pages should be in one Table tag, not broken into separate table tags on each page.
6. Not all images are figures
   • Just because something looks like an image doesn’t mean it should always be tagged as a figure.
   • Example: If an image only contains text (like a screenshot of a word), it can be inside a <span> tag with an ActualText attribute instead of a Figure tag.
7. Artifacts and real content
   • Some parts of a PDF (like decorative images, footers, or page numbers) are not considered real content.
   • These elements should be marked as artifacts so they don’t interfere with accessibility tools like screen readers.

Examples

The following table illustrates a few examples of incorrect and correct implementation of the content-tag-invalid rule:

How to fix

Follow these steps to fix any violations in the content-tag-invalid rule:

• Ensure all real content is tagged correctly based on its meaning, not just appearance.
• Use appropriate attributes depending on the context (e.g., textDecorationType for strikethrough text).
• Keep logically connected content together:
• Use one <table> tag for a table spanning multiple pages.
• Use one `<p>’ tag for a paragraph across columns or pages.
• Mark non-real content as artifacts.

Additional resources to fix issues

If you have created your PDFs using common tools like MS Word, Google Docs, or Adobe Acrobat, here are some resources to fix this issue in your tool of choice:

Adobe Acrobat

Adobe Acrobat Pro Accessibility Guide:

This guide explains how to tag elements (like headings, paragraphs, tables, and images), mark artifacts, and check accessibility.

Microsoft Word

Create Accessible PDFs from Word:

This guide explains how to use Word’s built-in accessibility checker and export a properly tagged PDF.

Add Alt Text to Images in Word:

Adding alt text ensures images are properly tagged when exported to PDF.

Google Docs

Make Google Docs Accessible:

This guide explains how to use headings, alt text, and other features to create accessible documents.

References

• ISO 14289-2:2024, Section 8.2.2 (Real content)
• ISO 32000-2:2020, Section 14.8 (PDF structure elements)
• ISO/TS 32005 (PDF 1.7 and PDF 2.0 structure rules)
• ISO 32000-2:2020, Section 14.8.2.2.1 (Definition of real content)