Native line numbering for Word (docx) output

[dhagmann]

Problem

Quarto has no built-in way to add line numbering to docx output, yet line numbers are a hard requirement for many manuscript-submission, legal, and peer-review workflows. Today the only recourse is to enable them by hand in Word after every render. The need was raised in discussion #6772 ("Adding line numbering to PDF and DOCX") — the PDF half was answered via the lineno package, but the docx half was never resolved.

Proposal

A format option to turn on continuous line numbering for docx:

format:
  docx:
    line-numbers: true

(Option name is the maintainers' call; it could eventually unify with PDF lineno and Typst's native line numbering into one cross-format option — what that discussion originally asked for. This request is scoped to docx, where there is no path today.)

Why this needs format-level support

Word stores line numbering as <w:lnNumType> inside a section's <w:sectPr>. The correct place for it is the document's existing main <w:sectPr> — the one that already carries the headerReferences and pgSz — so the running head and page size are preserved. A Lua filter/extension can't reach that section (it comes from the reference doc and is written by pandoc after filters run), so the most a filter can do is append a new section, which has no headerReference or pgSz and therefore drops the running head and resets the page size to Letter. Doing it correctly requires a format-level post-processing step on the written document.

[mcanouil]

@dhagmann Please read the guidelines in the future or more accurately tell your LLM to follow them.
Feature requests are to be made in the discussions.

Note also that Quarto is not writing almost all OpenXML code which is handled by Pandoc writer.

[mcanouil]

@dhagmann If you want line numbering, I suggest you enable it in a reference document as demonstrated in the documentation, see https://quarto.org/docs/output-formats/ms-word-templates.html.

1. Make sure you're in Print Layout view (View tab > Print Layout).
2. Go to the Layout tab.
3. Click Line Numbers in the Page Setup group.
4. Choose Continuous for numbering throughout the whole document, Restart Each Page to start at 1 on every page, or Restart Each Section to start at 1 after each section break.

Then in your Quarto document:

---
format:
  docx:
    reference-doc: custom-reference-doc.docx
---

{{< lipsum 3 >}}

Render it via quarto render document.qmd and you'll have line numbering. You can reuse the reference document as you see fit.