Groff (GNU troff) is a typesetting system that reads plain text mixed
with formatting commands and produces formatted output. Output may be
PostScript or PDF, html, or ASCII/UTF8 for display at the terminal.
Formatting commands may be either low-level typesetting requests
(“primitives”) or macros from a supplied set. Users may also write their
own macros. All three may be combined.
Present on most Unix systems owing to its long association with Unix
manuals (manpages), groff is capable of producing typographically
sophisticated documents while consuming only minimal system resources.