Mapping Screen to Printer

[Len Morgan]

I'd want to create a card that could be used as an ID Badge with a 
picture on it and the usual stuff like name, position, etc.  When I'm 
creating this card, how can I relate the size in the Object Inspector 
(which is in pixels) to the 2 1/8" x 3 3/8" dimensions of the physical card?

I guess to make the question even more general, how can I map from pixel 
dimensions to printer dimensions since I don't know (in advance) what 
the resolution of the printer is (or what it might be set to by the user).

Thanks!

len morgan