PDF Remediation: How to fix tables, Part 1

Sometimes, when we view a PDF table with Acrobat Pro's Table Editor tool, the red/purple lines that delineate the table cells don't align correctly.

Here's one way to correct this problem so that it doesn't throw off screen readers and other assistive technologies.

The problem: Acrobat's Table Editor doesn't identify the cells correctly

When a table doesn’t appear correctly in Acrobat’s Table Editor, the red/blue outlines and shading on the table cells don’t match the actual structure.

Expecting to see something like this:
Sample table viewed in Acrobat's Table Editor tool. The red and blue cells and lines correctly match the table's structure.

You may see something more like this:
Sample table that doesn't indicate the cell matrix correctly. Some cells appear to be merged in Table Editor when they aren't merged in the Tag tree.

This error prevents remediators from selecting the <TH> cells to add the required Scope and Span properties to them. It also causes the table to be mis-read by screen readers.

How to correct the problem

Instead of using Acrobat’s Table Editor, edit the <TH> and <TD> tags manually in the Tags Panel.

First, check that each cell in the table is correctly tagged as <TH> or <TD>.

  1. In Acrobat’s Tags panel, expand the <Table> tag and examine each <TH> and <TD>. Column Headers and Row Headers should have <TH> tags, and the remaining data cells should have <TD> tags.
  2. Modify any erroneous tag either by right-clicking on it and selecting Properties / Tags / Type, or by simply editing the tag itself.

Next, modify the attributes of each cell’s tag in the Tags panel. 

For each <TH> and <TD> cell:

  1. Right-click the cell and select Properties.
  2. Click the Edit Attribute Objects button.
  3. Click the New Item button, which will create /Attribute Object 1  <<Dictionary>>
  4. Click its + (plus sign) to open it.
  5. Click the /O  /Layout entry to highlight it and click the Change Item button.
  6. Change Layout to Table and click the OK button.

If the cell is a <TH> cell, set its Scope and Span settings

  1. Click on /Attribute Object 1  <<Dictionary>> to highlight it and click on the New Item button.
  2. In the Key: box, type in Scope
  3. In the Value: box type in either Column or Row, as appropriate, and select Name in the Value Type dropdown. Click OK.

If this <TH> cell spans more than one row and/or column:

  1. Click on /Attribute Object 1  <<Dictionary>> to highlight it and click on the New Item button.
  2. In the Key: box, type in either RowSpan or ColSpan as appropriate.
  3. In the Value: box, type in the appropriate number of cells spanned in that direction, and select Integer in the Value Type dropdown. Click OK.
  4. If both rows and columns are spanned, repeat steps 1 through 3 for the opposite span.

This method won't clear up your table's appearance in Acrobat's Table Editor, but it should now read correctly with screen readers. Before publishing the PDF, be sure to test your table with screen readers and other AT (assistive technologies.)

Check this blog for other tutorials on remediating PDFs.

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