SDF (Simple Document Format) is a freely available document development
system which generates high quality outputs in a variety of formats from
a single source. The output formats supported include PostScript, HTML,
POD, plain text, man pages, LaTeX, SGML, Windows help, MIF and RTF. If
the idea of specifying documents in a logical manner via a simple markup
language sounds appealing, SDF may be useful to you.

SDF documents are simple to create and maintain, minimising the time
spent on documentation. In particular, SDF directly supports the
creation and maintenance of large, on-line documentation systems
(including intranets) via centralised hypertext management and
rule-based hypertext generation.