Files suffixed with `.ps.gz' are Postscript files compressed with the gzip utility. Once they are uncompressed, they can be directly printed on a Postscript printer. If you do not have a Postscript printer, you can still look at the contents of the file with a Postscript previewer. You may want to look at the ghostscript software, available on this ftp site in /pub/ghost. Ghostscript allows you to preview Postscript files and to print them on non Postscript printers.