Well, I thought this would be easy, and maybe fun to set up. It wasn't....
I read the cups documentation ( http://www.cups.org/doc-1.1/sum.html#4_3_4
I installed a second instance of my printer (HPLJ6-4-up).
I opened a terminal window, and became root. I gave the command lpoptions -p HPLJ6-4-up -o number-up=4
I checked that this had worked:
[root@box root]# lpoptions -p HPLJ6-4-up
But when I print to this printer, the lights on the printer flash as the data is transferred to the printer, but then nothing
So I am as puzzled as you are. Maybe my cups is too old (V1.1.18)?
I will be interested in the solution if you manage to solve this problem!