I am going to explain this as if you have a nortel baystack 450, the only device I have mastered VLANs on. (if you can point me to a pdf of your switch I may be able to change the buzzwords)
in Nortel parlance the VLAN is what you listen to, and the PVID is what you send on.
you already have a VLAN 1 and every device there has a PVID of 1 and a VLAN 2 and every device there has a PVID of 2
Now you create a VLAN 3 and assign everyone to it. but do not change their PVIDs. your shared Printer gets a PVID of 3 and belongs to all 3 VLANs.
now the printer can chat to everyone and everyone can chat to the printer, but VLAN 1 and VLAN 2 are still seperate.
computers with PVID 1 can talk to VLAN 1 and the shared printer is part of VLAN 1
computers with PVID 2 can talk to VLAN 2 and the shared printer is part of VLAN 2
Only the shared printer can talk with PVID of 3 but everyone is part of VLAN3 so can hear it. I tried to remain child-like, all I acheived was childish.