GNU enscript is a free replacement for Adobe's Enscript program. Enscript converts ASCII files to PostScript™ and spools generated PostScript output to the specified printer or saves it to a file. Enscript can be extended to handle different output media and includes many options for customizing printouts.
enscript man page
http://people.ssh.fi/mtr/genscript/enscript.man.html
http://rpmfind.net/linux/rpm2html/search.php?query=enscript
Printing with formatted output
http://www.ncl.ac.uk/ucs/printscan/unix/formatted.html
Postscript Printing in UNIX
http://sandbox.aiss.uiuc.edu/oracle/nca/fnd/unix_ps.htm
CCIT Printing
http://www.u.arizona.edu/printing/prt-new.htm
want to create highlighting definitions for a new language or file format? See file /usr/share/enscript/hl/enscript.st for examples.