If we’re aiming to handle server-side printing, it looks like using CUPS is our best bet. It’s on our (long 
) list of stuff to look into.
From what I gather, you can shoot a PDF directly to a printer with the lp command. Another option could be converting the PDF to PostScript (maybe using GhostScript) and then sending it over to a PostScript compatible driver.
We’ll have to check out both methods, but right now, these seem like our top choices.