One often comes across a PostScript file generated by dvips which contains embedded PK fonts; if you try to generate PDF from such a file, the quality will be poor.
Of course, the proper solution is to regenerate the PostScript file, but if neither the sources nor the DVI file are available, one must needs resort to some sort of patching to replace the bitmap fonts in the file by outline fonts.
The program pkfix (by Heiko Oberdiek) will do this
patching, for files created by "not too old versions" of
dvips: it finds the fonts to be replaced by examining the
PostScript comments dvips has put in the file. For each
font, pkfix puts appropriate TeX commands in a file,
which it then processes and runs through dvips (with switch
-Ppdf) to acquire an appropriate copy of the font; these copies are
then patched back into the original file.
Yet another option is Frank Siegert's (shareware) PStill, which is capable of processing the PostScript it is distilling, and one option is to replace bitmap fonts in the file with Type 1 versions.
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=pkfix