printing pdf’s

I’m trying to print a pdf on a plotting machine for autocad users. 23 x 36 lets say. When I select a plotter that I want it doesn’t print the pdf? This particular machine only has 64 kbs of ram which can be the case, however, when us at the helpdesk print a large pdf, the job goes through without issue. These particular users who can’t print, 1 for sure is using Windows 2000 with adobe pro 6.0. We at the helpdesk have windows xp with adobe 7.0 I’ve checked the obvious things to see what is going on and still have had no luck with these users printing a pdf at a plotting machine. Any other suggestions?
Thank you