yepee !
One small step for the newbie, one giant step for Linux !
I solved all the problems with my printer. The last was with OpenOffice, which printed systematically in A5 format. Moreover I was unable to modify the options in the Mandrake Configuration Tool for my printer.
To solve the problem, I had to look after a very useful functionality in the MDK Config Tool : a log window which describes the commands while modifying the options. So I copied/pasted the command, and tested it, and guess what, it was buggy... Finally I adapted a working command (found for a useless printer called "Canon i250 version -something-" - my printer is simply called "i250" in the system), and now OOo documents are in A4 by default.
My conclusion : Boo-hoo-hoo ! Linux is not still adequate for pure office users !
But even though it is a bit stereotypical,
Linux Rules ! (at the moment)