Yes, it's that terrible problem -- what format shall I maintain the
manual in? In the academic community, everyone has access to LaTeX,
TeX, DVI and Postscript tools. In the gloomy world of home computers,
something had better be plain text or else it's not useful!
Here's a graph of "convertability" between various popular markup and
documentation formats (various other arrows could be added, but I feel
that e.g. TeX->HTML does a poor job of preserving the author's
intentions for any but the simplest of documents).
,-------------.
v |
,---> Plain text <----. | Plain text world
| ^ | |
| | | |
| Setext | |
| | | On-line document
Info <--- Texinfo ---------------> HTML | and Hypertext
| | Troff World
| | /
| LaTeX | / Lout
| | | | |
v v v v v
TeX ----> DVI -----> Postscript Typesetting world
It's clear from the diagram that if you want your manual to be available
both in on-line (and to be portable, that means plain text) format and
in pretty-printed paper format, *and* if you want to be able to maintain
it using just one source, then I suspect you're limited to Troff,
Texinfo and HTML.
I would recommend Texinfo, which can produce plain text, TeX and
hypertext (Info) documentation from one source file. Where the language
is inadequate to describe your document, you can present the same
material in both plain text and plain TeX; the former goes into the
online copy; the latter into the printed copy.
-- Gareth Rees