Hi Claude,
There is no built in way to backup print servers through DPM. What you will need to do is use a tool that comes with Windows. It is called
Printer Migration Wizard and Printbrm.exe (The command line version). These are migration tools but many use them to back up your printers. These tools will back up all of your printer settings and then you can back up the file it creates
with DPM.
I also have a blog post on this with more information:
http://www.buchatech.com/2009/06/migrate-printers/ .