How do I format/tag an accessible PDF table that spans multiple pages horizontally?

Question

I'm responsible for remediating a PDF that has been generated by a third-party, proprietary system for which I have no access to the layout or design. The goal is to pass the adobe acrobat DC accessibility checker before publication.

Some of the tables in the PDF span multiple pages horizontally (i.e. with a page break at column 4 of 7). Thus far, I have designated each piece of text content as a "Cell" and grouped those into a "Table Row" tag and defined each header and sub-header as a "Table Header Cell".

However, Acrobat DC seems to get confused as to the relative size and spacing of each table element. It is creating phantom column headers and rearranging or combining rows in order to fit the appearance of a more standard layout PER PAGE. But since I need one cohesive table to span TWO PAGES, this is breaking my accessibility.

Depending on how I nest my table elements, I get a table layout like one of the two examples below:

Example when including blank cells for multi-column header rows

Example when defining the column span of multi-colum header rows as "7"

As you can see, the layout is not uniform and does not pass regularity checks. Plus, as I add more rows with several blank cells, the table editor produces an error that reads: "Unknown Table Structure Encountered"

The only way I have managed to remove this error, is to exclude the bolded main-section sub-headers from the tag structure entirely, but I cannot just leave them as untagged content and pass the checker.

Please help.

Answer 1

Signed up just to comment to

Kevin, thanks for replying. Because of the malformed grid, I cannot even click on the cells on Page 2 in order to associate headers. Is there a way to define table structure without using the Table Editor mode? – Glamador Apr 3 at 12:27

but don't have the rep yet to do so:

Glamador - Knowing it can't help you half a year ago but might in the future: I encountered this in a document this week and figured out the "Why" and how to get the Table Editor back, but not the "Easiest/best way to solve" the tagging in Acrobat. This issue is denying you Table Editor is with the table header (TH) cell you created that spans multiple pages.

So if you set a table header cell to something like Row Span: 7, and 3 of those are on the second page Acrobat will give you the "Unknown table structure encountered. Please retag this table using the Reading Order Tool to possibly fix the problem." error any time you try to use the Table Editor on the table that has that [table header cell with a multi-page row span/I'm not working with but assume column span too].

To get your Table Editor use back (not solving the tagging of accessibility, but to quit getting that error on your table,):

1. Go to your tags
2. Create a new empty Table Header Cell
3. Drag the content displayed in the tag from the problem TH to your new TH
4. Delete the [multiple page row/column spanning, but now empty] problem TH
5. Repeat if you did this in multiple TH in the same table
6. You can now use Table Editor again

Note: Because you can't use the Table Editor once these problem headers have been created you can't use it to see which TH's you have set to span multiple pages, or see those row/column spans, so you're going to have to just look at your document if you went through tagging and are going back and checking later and figure out which are the likely problem headers to replace. If you create that header span again in the table that goes across multiple pages you'll be unable to use the Table Editor again until you delete that tag with the page spanning issue.

I haven't found if you can combine TH Row Span settings with IDs/Associated Header Cell IDs and have the user software identify both, so I've been doing the tedious ID association on large but simple tables as my "It's tagged correctly" option, but unfortunately it isn't nearly as fast and easy as Row Spans.

Answer 2

You can edit the tag's object properties by right-clicking on the tag and then you can add an ID there if it doesn't already have one. Be sure each data cell is associated with a header cell. PAC's screen reader preview will also give a good view of the layout to help you get everything associated correctly.