PDF Error Handling Encyclopedia

Not Checked By Adobe Acrobat

Adobe Acrobat's accessibility checker is great, but is incomplete. There are some checks that need to be done manually, that are often forgotten because Adobe's checker doesn't remind users to check them. 

Improperly tagged table of contents

If your document contains a table of contents, but it is not tagged as a <TOC> in Adobe Acrobat's Accessibility tags sidebar, you should review your source document (Microsoft Word document or Google Doc) to ensure the table of contents tools is being used. If you don't have the source document, you can tag the table of contents from scratch.

List and TOC spanning multiple pages

If you have converted from a Microsoft Word document or Google Doc, often list tags <L> that span multiple pages, will be broken into multiple lists in the Accessibility tags tree, one on each page. The same issue arises with table of contents <TOC> tags that span multiple pages.

In the image below: the list items <LI> before the page break are tagged in a separate list <L> from the items after the page break.

To fix Lists or TOCs spanning multiple pages,

1. Identify any lists or tables of contents that span multiple pages, and find their tags in the Accessibility tags sidebar.
2. Open each list tag <L> or table of contents tag <TOC> (using the caret next to it).
3. Select all the list items <LI> (or table of contents items <TOCI>) from the second list <L> (or table of contents <TOC>).
4. Drag the selected items below the last list item <LI> (or table or contents item <TOCI>) in the first list <L> (or table of contents <TOC>), making sure to keep the items in order.
5. Once you have emptied the second list <L> of all list items <LI> or table of contents <TOC> of all table of contents items <TOCI>, you can delete the empty tag.
6. If the list or table of contents spans more than one page break, repeat steps 1-4 until there is only one list tag <L> or table of contents tag <TOC>.

Missing document root

Sometimes a document contains all the 

Tables used for layout

Often, document creators like you may prefer the look of using a table for their document's layout. This is fine visually, but since tables are semantic elements, this practice can be confusing for people that use screen readers to perceive your document. You don't need to change anything visually, but the tag tree should be updated to remove the table tag.

In the image below, I've selected all paragraphs <P> nested in a table tag <Table>.

To fix Tables used for layout, 

1. Identify any tables in the document that are not used for data, and find their tags in the Accessibility tags sidebar.
2. Open the <Table> tag, the <THead> and <TBody> within (if present), all table rows <TR> within those, and each table header cell <TH> and table data cell <TD> within each row to show the contents of the table.
3.   If the contents of this table are bare text tags, you will need to create new paragraph tags <P> to contain them (or convert the <TH> or <TD> containers to <P> tags). All bare text tags require container tags. 
4. Select all the contents of the table (Hold CTRL +click). This can be done a few at a time if that's easier. Make sure to select all the table's contents, it will be deleted later.
   Note: Some contents may not be within <TH> and <TD> tags. I have seen <P> tags at the <TR> level at times, select those too.
5. Drag all selected tags above the table tag <Table> in the tag tree.
6. Delete the empty table tag <Table>. All contained <THead>, <TBody>, <TR>, <TH>, and <TD> tags will be deleted as well.

Adobe Acrobat Accessibility Checker

Learn how to find and run Adobe Acrobat's Accessibility Checker on our help page:
PDF Remediation in Adobe Acrobat Pro

Unsure about failed checks in Adobe Acrobat's Accessibility checker? Check out their help page: Create and verify PDF accessibility (Acrobat Pro), or right click on the failed check and choose the "Explain" option to learn more about that specific issue. 

The "Fix" option is only present on some checks. While it may look like a great single click solution, there are sometimes issues with this option. Even if this option is available, make sure you understand what is being fixed. If have any issues, consult the guide below for more information on the specific issue that needs to be fixed.

The "Check Again" option only re-checks one issue, rather than running the full accessibility check again. This option is great to see if a change you made had the intended affect.

Document

Image-only PDF

If you're dealing with an image-only PDF, you probably don't have access to a viable source document to fix the issue there. For this reason, we recommend using Adobe Acrobat's optical character recognition (OCR) tool to identify text within the image.

1. Go to All Tools > Scan & OCR > In this file > check All Pages > Recognize text

  This can also be fixed using the "Fix" option from the issue context menu.

  If you go to All Tools > Edit a PDF, Adobe Acrobat may automatically convert any recognized text into editable text. However, in doing so this, you may end up changing the font of some of that text, throwing off the visual style of the document. To avoid this, always run the "Scan & OCR" tool before "Edit a PDF".

Tagged PDF

This means your document doesn't have any accessibility tags at all. Run the autotagger to get started fixing this issue:

1. Go to All Tools > Prepare for accessibility > Automatically tag PDF

  This fix will create tags, but they may not all be perfect. Always check the Logical Reading order manually after using the autotagger.

  You can try using the "Fix" option from the context menu, but we've experienced issues with this option in the past, specifically that the visual style of the document is altered by this action. If this happens, you may need to close without saving to revert to a previous version, or remediate the visual style of the document. 

Logical Reading Order (Manual check)

Adobe Acrobat's accessibility checker reminds you to manually check the reading order of your document's tag tree every time it is run. Though it doesn't present an error, it does present a warning as a reminder to perform this vital check manually. To perform this check,

1. Open the Accessibility tags sidebar. The icon for this sidebar looks like a luggage tag. If you don't have this sidebar option, right click your sidebar and make sure it is checked in the context menu (see image).
2. The tag tree should consist of a Tags root, containing a <Document>, which should contain all other tags in the PDF. 
   Note: The caret next to each tag opens it. If there is no caret, it is empty.
3. Start at the top tag and use your keyboard's down arrow to highlight each tag in sequence. Each element should be highlighted in your document in the appropriate order. It is wise to open container tags like lists <L> and tables <Table> to ensure the contained items are in the correct order as well.
   This phase of checking the document is also a great time to review your headings.
4. If everything is in the correct order, your check is complete.

Primary Language

This issue is safe to use the "Fix" context menu option on. To double check that the document language is correct, 

1. Right click anywhere on the document and go to Document properties in the context menu,
   OR
   Go to Menu > File > Document properties
2. Go to the Advanced tab and update the language in the Reading Options section

Title

1. Right click anywhere on the document and go to Document properties in the context menu,
   OR
   Go to Menu > File > Document properties
2. Update the Title field to something readable by humans (not a filename with dashes and underscores between the words).

  The title is important for the visual presentation of your document as well, it appears in the top of almost every PDF viewer (example image, Google Chrome):

  You can try using the "Fix" option from the context menu, but we've experienced issues with this option in the past, specifically the title field is filled with the file name, so its best to review this manually.

Bookmarks

 

Page Content

Tagged Content

Tagged Annotations

Tab Order

Character encoding

Navigation Links (manual check)

Forms

Tagged form fields

Field descriptions

Alternate Text

Figures alternate text

Nested alternate text

Other elements alternate text

Tables

Rows

TH and TD

Headers

Regularity

Summary (optional)

 

Lists

List items

Lbl and LBody

 

Headings

Appopriate nesting