508 PDF Help Center


This 508 PDF Help Center lists many of the common errors and warnings encountered when using the popular free PDF Accessibility Checker (PAC) from Access for All, along with suggestions for resolving the errors and warnings using Adobe Acrobat Professional. PAC 2 was the first automated checker for PDF/UA compliance, and its successor, PAC 3, remains – in my opinion – the best one. The suggestions are specific to Acrobat Professional XI or, in some cases, DC, for Windows. The concepts should apply when using other versions, but the specific location of tools and features within Acrobat Pro may vary.

PAC 2 / PAC 3 Errors and Warnings

The following common PDF accessibility errors and warnings are shown in the order they are presented in the PAC 2 accessibility report, when sorted by Title. Click on a specific error or warning for details including suggestions for remediation using Adobe Acrobat Professional XI.

PDF/UA | Basic Requirements | Content | Artifacts and tagged content

Artifact present inside tagged content

Tagged content present inside an Artifact

PDF/UA | Basic Requirements | Content | Tagged content and artifacts

[X] object not tagged

PDF/UA | Basic Requirements | Fonts | Font Embedding

Font not embedded

PDF/UA | Basic Requirements | Natural Language of [X]

Natural language of [X] cannot be determined

PDF/UA | Logical Structure | Alternative Descriptions | Alternative descriptions for annotations

Alternative description missing for an annotation

PDF/UA | Logical Structure | Role mapping | Role mapping for standard structure types

Standard structure type [X] is remapped to [Y]

Structure type [X] is mapped in a circular fashion

PDF/UA | Logical Structure | Role mapping | Role mapping of non-standard structure types

Non-standard structure type [X] is neither mapped to a standard structure type nor to another non-standard structure type

PDF/UA | Logical Structure | Structure Elements | Annotations | Nesting of Link annotations inside Link structure elements

Link annotation is not nested inside a Link structure element

PDF/UA | Logical Structure | Structure Elements | Figures | Bounding Boxes

Figure element on a single page with no bounding box

PDF/UA | Logical Structure | Structure Elements | Headings | Nesting of heading levels

Numbered heading skips one or more heading levels

PDF/UA | Logical Structure | Structure Elements | Notes | ID entry in Note structure elements

ID missing in Note structure element

PDF/UA | Logical Structure | Structure Elements | Tables | Table regularity

Irregular table (missing cell)

Irregular table (span attributes)

PDF/UA | Logical Structure | Structure Tree | Document structure elements

Document structure element found which is not a root element

PDF/UA | Logical Structure | Structure Tree | [X] structure element

[X] structure element used as root element

Possibly inappropriate use of a [X] structure element

PDF/UA | Metadata and Settings | Document settings | Display of document title in window title

DisplayDocTitle key is not set to true

PDF/UA | Metadata and Settings | Document settings | Tag suspects

Suspects key is set to true

PDF/UA | Metadata and Settings | Document settings | Tab order entry in page with annotations

Tab order entry in page with annotations not set to S

PDF/UA | Metadata and Settings | Metadata | “dc:title” in document’s XMP metadata

“dc:title” entry missing in document’s XMP metadata

PDF/UA | Metadata and Settings | Metadata | PDF/UA identifier | PDF/UA identifier

PDF/UA identifier missing

Errors Requiring Human Inspection

The following common PDF accessibility errors are not detected by PAC – human inspection is required.

ListNumbering attribute for ordered list

Header and footer artifacts

Table header cell not tagged as a header

Non-table content tagged as a table

Complex table header IDs

Z order problem

Actual Text with null string

Actual Text – Alt Text – Expansion Text – Contents Key

I ran out of heading levels!

Insufficient contrast for text


Dealing with Form XObjects