Matterhorn 04-001 · PDF/UA-1 UA1:7.1-6

Red means overdue: meaning a PDF's tags don't carry

Red text meaning "overdue", bold meaning "required", indentation meaning "sub-clause" — visual encodings that carry meaning must also exist in the tag structure or in text.

What a screen reader actually does

The meaning is invisible. A row highlighted in red as "non-compliant" reads identically to every other row.

What the condition covers

Any time the look of something tells a sighted reader what it means, the same meaning has to exist where a screen reader can get it: in the text, or in the tags. The protocol lists four carriers — contrast, colour, format and layout — and in real documents they look like this:

The last column is the condition. In each row the information exists only in a property the structure tree does not carry: fill colour, a line drawn through text, a font weight, a left margin.

Two requirements, not one

PDF/UA-1 frames this as a tagging requirement: the content has to be tagged to reflect all the meaning the visual treatment conveys. WCAG 1.4.1, which the same failure usually breaks, frames it visually: colour must not be the only visual means of conveying the information.

The difference matters at repair time. A structure-only fix — alternate text on a span saying “overdue”, for instance — gives a screen-reader user the meaning and satisfies the PDF/UA side. It does nothing for a sighted reader with a red–green colour deficiency, who looks at a column of identically coloured dates. A visible fix, a word or a symbol added to the page, satisfies both.

Where it comes from

• Spreadsheets with conditional formatting. Excel colours a cell and the colour is the whole message; exporting to PDF keeps the colour and nothing else. The Excel export guide covers the rest of that route.
• Tracked changes and redlines. Word can print markup, and the deletions arrive as struck-through text with no structural difference from the text around them.
• Forms that mark required fields in bold or red, or with an asterisk whose key is at the foot of the page.
• Charts whose legend is a coloured square and a series name, with the lines distinguishable only by hue.
• Layout used as structure: indentation for clause hierarchy instead of nested lists, a two-column “before / after” arrangement instead of a table.

How to check it free

This is a judgement a person makes, and the method is a comparison: what the page shows against what the text and tags say.

1. List the visual encodings. Go page by page and note every colour, weight, decoration and offset that is not just styling. Ask of each one: if this were gone, would a reader lose anything?

2. Strip them and read what is left. Adobe documents a viewer setting that does the stripping for you: Preferences → Accessibility → Replace Document Colors → Use High-Contrast Colors (Adobe: Create and verify PDF accessibility). With it on, text is drawn in the colours you chose rather than the document’s — the view a reader who overrides colours actually has. Whatever meaning vanishes with the document’s colours is a candidate for this condition.

3. Read the structure as text. Poppler’s free pdfinfo prints the tag tree with the text inside each element and whatever attributes the producer wrote — which describe layout, not meaning:

   $ pdfinfo -struct-text report.pdf
   Document
     P (block):
        /Placement /Block
        /SpaceBefore 0.24
       "Quarterly Accessibility Report"
     H2 (block):
        /Placement /Block
        /SpaceBefore 0.483
       "Summary of findings"

   If the meaning is not in that output, a screen reader has nothing to announce it from. Acrobat’s Save as accessible text gives a similar plain view.

Acrobat’s Accessibility Checker has a Color contrast rule. Adobe’s guidance for it points at WCAG 1.4.3 — contrast — which is a different requirement from this one (contrast in PDFs has its own guide); passing it says nothing about whether colour carries meaning.

How to fix it free

In the source document, which is where it belongs.

• Add the meaning in words: a Status column that says Overdue; (required) in the label; Deleted: before a struck clause, or a separate list of deletions.
• Use structure for structure: nested numbered lists for sub-clauses, a real table for a before/after comparison, the form tool’s own required setting for required fields.
• For charts, label the lines directly or add markers and patterns, and say in the figure’s alternate text what the chart shows rather than what colours it uses.

Then export again with tagging on.

In Acrobat Pro, when the source is gone, the structural half can be done in the Tags panel. Adobe’s documented route for adding a spoken expansion to a piece of text — written for abbreviations — is to select the element, choose Properties from the Options menu, open the Tag tab and type into Alternate Text (Adobe: Edit document structure with the Content and Tags panels). Alternate text replaces what is read for that element, so it must include the visible text as well as the meaning: 12 May, overdue, not overdue. For a chart, the same panel or All tools → Prepare for accessibility → Add alternate text puts the description on the <Figure>. None of this changes what a sighted reader sees, so the WCAG half is still open until the source is fixed.

What Taggart does

Taggart has no check for this condition. Nothing in its checks reads fill colour or text decoration, so a red status column or a struck-through clause passes every check it runs, and the condition does not appear in the findings or the review queue. It is on the list of conditions Taggart does not check: the conformance claim stops at machine checks passed until a person confirms that list — a checkbox in the application — and only then is the PDF/UA identifier written. The confirmation covers the whole list at once and records that it was given, not what was found, so the comparison above is what stands behind it.

The one place Taggart reads appearance is the heading heuristic behind 14-001, which counts lines that are larger than the body text, or bold and short, and reports when a document has far more of them than it has heading tags. That is one specific case of this condition — format meaning heading — and it is the only one Taggart looks for.

Two other things bear on it. Taggart’s screen-reader preview shows the document as the structure tree presents it — text in reading order, role announcements, alternate text, and no colour — which is a convenient version of step 3 with the page beside it. And its repairs are built not to change what a page looks like; the service re-renders every repaired file and compares it with the original. That guarantee is also the limit here. The visible fix this condition usually needs — a word on the page where there was only a colour — is a change Taggart is built not to make, so it has to happen in the source document.

How Taggart handles it

No software can decide this one, and Taggart has no check for it, so it never appears among the findings or in the review queue. It is on the list of conditions Taggart asks you to confirm by hand before it writes the PDF/UA claim into the file — the claim waits until you have.

Where this sits in the standards

Related conditions

• 01-006 Structure type is not semantically appropriateThe tag does not match the nature of the content: a heading tagged as a paragraph, a data table tagged as a layout container, a caption tagged as body text. This is the judgment call that no validator can make for you.
• 13-004 Figure tag alternative or replacement text missingA Figure element has neither /Alt nor /ActualText. Every Figure must have one or the other; if the image is decorative it should be an artifact instead of a Figure.
• 15-002 A column has a header cell, but that header cell is not tagged as a headerThe top row labels the columns but is tagged as ordinary data cells.
• 28-005 A form field has neither a TU entry nor an alternative descriptionThe /TU tooltip is the accessible name of a PDF form field. Without it the field has no name at all — the visible label printed next to it is not connected to the control.

Other conditions in checkpoint 04

Checkpoint 04 covers color and contrast. These are its other failure conditions; the ones without a link are in the rule set but do not have a written page yet.

This condition needs a person’s judgement, so there was nothing for a tool to check. Written from ISO 14289-1 and the Matterhorn Protocol on 2026-10-02. The Acrobat steps follow Adobe’s documentation and were not walked through by hand. Last updated 2026-10-10.