Psroff is a suite of programs that allow you to translate CAT troff
output or ditroff output format into PostScript, HP Laserjet (with
incremental font downloading) or ditroff.  See description of hp2pbm
below for driving printers other than these three.

Psroff works with all versions of CAT troff and ditroff, including
groff.  Psroff allows you to change fonts on the fly (unlike any other
CAT troff converter).  Psroff has been used to drive HP Laserjet and
clone printers, PostScript (including Display PostScript and Sun
Pageview), X windows previewers (such as xditview and xtroff),
Ghostscript and many others.

Psroff comes with a large suite of utility programs that allow you to
create, manipulate, display HP Laserjet and PostScript fonts, as well
as construct width tables for these fonts from a variety of sources,
including TeK PK format, HP SFP, and PostScript.  Psroff also comes
with a number of other utilities, such as PostScript page reordering,
Ascii-2-PostScript converters etc.  Psroff 3.0 is the only troff HP
Laserjet filter fully supporting scalable fonts or HPGL/2 graphics on
HP LJ III printers.

Psroff 3.0 is capable of performing some limited emulation of ditroff
features (eg: line drawing) with CAT troff.

Psroff 3.0 is available from comp.sources.unix, volume 24.  Or from
ftp.uunet.ca, in /distrib/chris_lewis/psroff3.0pl17 (fully patched).
Patch level 17 is current.  The author is Chris Lewis,
clewis@ferret.ocunix.on.ca.

Adobe Transcript is a commercial package similar to psroff, in that it
contains filters for converting ditroff or CAT troff.  But only to
PostScript.  It also contains filters for Ascii-2-PostScript, and is
often installed as part of SunOS printcap filters.  Adobe Transcript
contains a user interface script called "psroff" which should not be
confused with the other psroff (but often is).  Information can be
acquired on its availability by contacting the Qualix group at
1-800-245-UNIX, or info@qualix.com.  Supports psfig with a little
hacking (instructions in psfig release).

The groff package from the Free-Software-Foundation includes drivers
for PostScript, DVI, X and constant-width printers, and the complete
suite of troff preprocessors with the exception of grap.  It is
available via anonymous ftp from several sources (it needs the FSF C++
or AT&T C++ 2.0 compilers to compile, but many binary versions are also
available for FTP).  Supports character kerning (unlike CAT troff or
DWB).  Does not contain an HP Laserjet driver.  A "dvi2lj" or psroff
3.0 can be used as a HP Laserjet driver for groff.  Groff has made some
slight changes in the ditroff and width table formats, so use with
non-groff drivers may need a little fiddling.  Written by James Clark.
The latest version can always be ftped from prep.ai.mit.edu:pub/gnu.

James has just updated groff to support HP Laserjet 4 printers in
PCL5 (as opposed to PostScript) mode utilizing the scalable fonts
built into the printer.  This apparently also works on Laserjet 3
printers, with some minor deficiencies in graphics support, and not as
many fonts.  Will not work on HP Laserjet II printers, and apparently
cannot work with non-scalable or downloaded fonts.  The LJ4 software
can be found in: ftp.jclark.com:/pub/test/groff-lj4.tar.gz.

It's worth noting that there is a major difference between driving
HP Laserjet 3 or 4 (PCL5) and driving HP Laserjet 2 (PCL4).   PCL5
has scalable fonts, and an implementation of HPGL/2 - HP's graphics
language.  Driving PCL5 is fairly easy.  PCL4 doesn't support scalable
fonts or graphics, and they have to be simulated by downloads and
raster graphics.  A full feature driver for PCL4 will also work on PCL5,
whereas something taking advantage of PCL5 won't work on PCL4.  Groff
only supports PCL5.  Psroff has full function drivers for both PCL4
and PCL5.