Guide

How to tag a table in a PDF for accessibility

Table structure, header scope, and the point where Scope stops working and Headers references become necessary.

About 18 minutes · involved

The grammar

ISO 32000-1 Table 337 defines what may contain what, and it is short:

Table
├── Caption          (optional, first)
├── THead → TR → TH
├── TBody → TR → TH | TD
└── TFoot → TR → TH | TD

TR may only appear in Table, THead, TBody or TFoot. TH and TD may only appear in TR. Anything else is condition 09-004, and Acrobat’s Table Editor will refuse to open a table whose grammar is broken — which is a useful diagnostic in itself.

Headers, in two ways

/Scope on each TH: Row, Column or Both. Sufficient for a regular grid.

/Headers on each data cell: an array of /ID strings naming the headers that govern it. Necessary once the table is irregular.

You must use one or the other. A TH with no /Scope in a table with no /Headers is condition 15-003.

Doing it free, in Acrobat Pro

1. Tags panel → find the <Table> → right-click → Table Editor. If it is greyed out, the grammar is broken. Fix that first.
2. The page shows a coloured grid. Red is TH, grey is TD.
3. Any header showing grey: right-click → Table Cell Properties → Type: Header Cell.
4. Set Scope in the same dialog.
5. Shift-click a run of cells in one row to set them together — this is the one place Acrobat gives you multi-select and it saves real time.
6. For complex tables, use Associated Header Cell IDs in the same dialog, one cell at a time.

Step 6 is where a 5×20 table becomes 100 dialogs. There is no free way around it.

Upstream is dramatically faster

Word: select the header row → Table Tools → Layout → Repeat Header Rows, and tick Repeat as header row at the top of each page in Table Properties. Word exports it as TH with /Scope /Column already set.

InDesign: Table → Convert Rows → To Header.

Both take seconds and survive the next revision. If you have the source, this is not a close call.

Where Taggart fits

Setting /Scope on cells that are already TH is mechanical, and Taggart infers the right value from position: a cell in an all-TH row heads its column, a leading cell in a body row heads its row, a corner cell in a stacked header gets Both. That ships in “Fix All Safe”.

Promoting a TD to a TH is a claim about what the document means, so it needs your approval.

And Taggart detects the case where /Scope is not enough — spanning cells or stacked header rows — and reports it as 15-005 rather than writing a /Scope that would look conformant and still mislead a reader.

Related failure conditions

• 15-003 A TH cell does not contain a Scope attribute Header cells must declare whether they head a row, a column, or both, unless the table instead uses explicit /Headers ID references on every data cell.
• 15-005 A given cell's header cannot be unambiguously determined In a complex table — merged cells, stacked header rows, split spans — Scope alone cannot express the associations, so explicit /Headers references are required.
• 15-001 A row has a header cell, but that header cell is not tagged as a header The leftmost (or, in RTL, rightmost) cell of each row labels the row but is tagged TD instead of TH.
• 09-004 A table-related structure element does not conform to ISO 32000-1, Table 337 The table grammar is broken: a TD outside a TR, a TR outside Table/THead/TBody/TFoot, a Table with no rows.

Last updated 2026-09-08 .