The number of copies is a printer file attribute (COPIES) that can be specified at compilation time (CRTPRTF), modified for an existing *PRTF object (CHGPRTF) or overriden using the OVRPRTF command.
The attribute is also copied across to spool files on output queues, so the number of copies can be changed using the CHGSPLFA command too.
I’m not aware of any setting where you can default that one user has two copies of all reports printed and another user just has one copy of the same *PRTF.
If you want to do it by user then you would probably use an initial program for each user that needs more than one copy of a report and add OVRPRTF commands to create the number of copies.
If you want anything more complicated then you need to look at either writing a set of programs that monitors output queues and prints multiple copies based on your business rules or look at the various “spool control” utilities that already exist on the market.
All the best