# What language, text-direction and Unicode-mapping information can a PDF carry, and what do PDF/A and PDF/UA validators actually check about it?

- id: art_01M5MV8W3WK17E4CAYGTM93F9M
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T17, T20 · tags: none
- updated: 2026-10-23T16:59:55.382Z
- url: https://veyrul.com/articles/art_01M5MV8W3WK17E4CAYGTM93F9M

ISO 32000-1 (PDF 1.7) lets a PDF set a default language in the document catalogue (Lang), override it on structure elements and on marked-content Span sequences, and even inside text strings via a language escape; the empty string means unknown, and tags are cited as RFC 3066 language tags (RFC 5646 says RFC-3066-valid tags remain valid). Direction is a separate Tagged PDF layout attribute (WritingMode). veraPDF's machine-readable rules show that PDF/A-2 Level A checks the Lang string syntactically (regex), PDF/UA-2 requires a non-empty catalogue Lang, and PDF/A-2 Level A/U requires a Unicode map for every font. None of the inspected rules checks that the declared language matches the text or the font's coverage.

ISO 32000-1 (PDF 1.7) lets a PDF set a default language in the document catalogue (Lang), override it on structure elements and on marked-content Span sequences, and even inside text strings via a language escape; the empty string means unknown, and tags are cited as RFC 3066 language tags (RFC 5646 says RFC-3066-valid tags remain valid). Direction is a separate Tagged PDF layout attribute (WritingMode). veraPDF's machine-readable rules show that PDF/A-2 Level A checks the Lang string syntactically (regex), PDF/UA-2 requires a non-empty catalogue Lang, and PDF/A-2 Level A/U requires a Unicode map for every font. None of the inspected rules checks that the declared language matches the text or the font's coverage.

Curator qualifications: PDF Lang at catalogue, structure element and marked-content Span; inheritance; empty = unknown; RFC 3066 cited. veraPDF rule texts not located among decoded copies (producer read them from the repo).

Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/PDF32000_2008.pdf",
      "note": "ISO 32000-1 14.9.2.2 (layout text L40516-L40517; uncompressed sha a6b31f4f matches producer list)"
    },
    {
      "url": "https://www.rfc-editor.org/rfc/rfc5646.txt",
      "note": "ISO 32000-1 14.9.2.2 (layout text L40516-L40517; uncompressed sha a6b31f4f matches producer list)"
    },
    {
      "url": "https://github.com/veraPDF/veraPDF-validation-profiles/tree/b76c28ff0d8809c30c4d0e64dc6c393f3c9019dc",
      "note": "ISO 32000-1 14.9.2.2 (layout text L40516-L40517; uncompressed sha a6b31f4f matches producer list)"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] ISO 32000-1 (PDF 1.7) lets a PDF set a default language in the document catalogue (Lang), override it on structure elements and on marked-content Span sequences, and even inside text strings via a language escape; the empty string means unknown, and tags are cited as RFC 3066 language tags (RFC 5646 says RFC-3066-valid tags remain valid). Direction is a separate Tagged PDF layout attribute (WritingMode). veraPDF's machine-readable rules show that PDF/A-2 Level A checks the Lang string syntactically (regex), PDF/UA-2 requires a non-empty catalogue Lang, and PDF/A-2 Level A/U requires a Unicode map for every font. None of the inspected rules checks that the declared language matches the text or the font's coverage. · locator: ISO 32000-1 14.9.2.2 (layout text L40516-L40517; uncompressed sha a6b31f4f matches producer list) · source: https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/PDF32000_2008.pdf

Rights:
- documentation: license=unknown hosting=permitted redistribution=permitted modification=unknown training=unknown · Applies to this original summary only, not to the cited sources.

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