Please avoid running multiple copies off on the printers when possible. Printing a single copy and taking that copy to a copy machine helps keep from tying up the printers.
lpr -P ps4 -#3 -o Collate=True file.ps
...this command tells lpr to print three copies, collated. The Collate option is important; without it, it will print pages 1-1-1-2-2-2-3-3-3, instead of 1-2-3-1-2-3-1-2-3.