How can I add font in postscript 3 printer ?

For most PostScript printers, especially those that don't have writable file systems (i.e., disks), you generally cannot add to the collection of resident fonts. Yes, you can write some custom PostScript that you can send to a printer to download a font “outside the server loop” but such fonts will typically disappear with every power cycle.

Since the mid-1990's, operating systems, i.e. MacOS and Windows, and most high end applications simply include fonts within the generated PostScript stream. The original reason for trying to add resident fonts was that typical host computer / printer interfaces were exceptionally slow (RS232 serial for example at 9600 baud and early parallel ports weren't much better). But today's garden variety USB connection not to mention Ethernet and WIFI connections make this concern about download time irrelevant. And typical drivers and applications don't download entire fonts, but rather subsets of glyphs actually needed in the PostScript job.

Bottom line, unless you have some very unusual and specialized requirements outside of normal MacOS and Windows applications and their drivers, you are better off letting the PostScript drivers and applications assume that there are no printer resident fonts and do incremental download of all fonts needed for a print job from the host-based fonts. (Note, one big problem encountered in the past was that printer-resident fonts were often out of sync with updated host-resident fonts.)

          - Dov