Compositing it on your server sounds like the best bet, and it could be done as-is, in pdf, or using image compositing software.

Or, if you've eaten a bowl of hot peppers and feel antsy, you could write a Perl client application which does this on their computer. Hard to tweak though. Been looking at Ch. 5 of Windows NT Win32 Perl Programming: The Standard Extensions by Dave Roth. (My New Years present to myself).

Looks like M$ published an OLE reference to Office 97 which conceivably could help you find out how their printer is set up. Likewise you could write an ActiveX in Perl that does this task. Same book tells all (well, much) Nothing in it about printers per se, though there is stuff about accessing shares. I think this is frontier stuff cowboy..

Well, I just googled with keywords OLE printer margin. Hmm, first hit gives me "XL.ActiveSheet.PageSetup.LeftMargin = 18"! Run that through the mixer! Add the keyword "automation" and there's a lot more links to go through.

Finally I found something called "HOWTO: Use a VB ActiveX Component for Word Automation From Internet Explorer (Q286023)". Huh. M$ says it is a good way to get load off the server. Anyway, seems like this could be done in Perl too.

Of course this is totally useless if your customers are on Linux which is happening a bit more rapidly these days. Server side maybe is the safest since you don't have to wrestle with possibly badly documented object models etc.