make groff -Tpdf the default pdf-engine for the ms format

[lodwicz]

As referenced before, and upon suggestion of @jgm , I'd like to point out that groff stopped maintaining/distributing pdfmark/pdfroff since 1.24.0, 2026-02-28, which is now maintained and distributed separately, to favor the still supported -Tpdf flag, which calls the Perl script gropdf for similar purposes.

Thus, it seems to me that the groff should be the default pdf-engine for the ms format, which along with man is the groff macro package supported by pandoc.

pdfroff requires ghostscript to postprocess groff's native postscript output, which has ensued a discussion on the pdfmark-groff repo, while gropdf requires Perl; so both have extra requirements besides groff itself to produce PDF. This and other issues may need to be discussed before making a decision.

An issue has already been created related to this discussion, as I did not know exactly how to handle my proposal.

[jgm]

I think this makes sense, but I'd like to get comments from others who use the ms backend. One drawback is that groff does not provide the option to relocate the table of contents to the beginning of the document, as pdfroff does. There may be other differences as well.

[lodwicz]

I think this makes sense, but I'd like to get comments from others who use the ms backend. One drawback is that groff does not provide the option to relocate the table of contents to the beginning of the document, as pdfroff does. There may be other differences as well.

I don't know if pdfroff is that reliable even on that respect: in many of a test the --toc option does indeed add a toc at the beginng of the document, but somehow adds an extra page (a cover page, I assume), it fumbles pagination, and does not report section headings text. the --pdf-engine-opt=--no-toc-relocation simply omits the toc.

On the other hand, the alternative groff -Tpdf does indeed keep the toc at the end of document, as does groff by design for all other output devices, but keeps the section headings text, and produces a smaller PDF.

[jgm]

I'm going to make the change.