I solved that on my home net - where I initialy had the printer (Airprint + IP) on the outside (WAN) of the PFSense box.
Install Avahi, description below. Avahi should allow the required broadcasts/multicasts across VLANS/Interfaces:
Avahi net 2.1_1 Avahi is a system which facilitates host and service discovery in local networks via mDNS (Multicast DNS) and DNS-SD (DNS Service Discovery). This package allows mDNS/DNS-SD protocols to work across multiple LAN segments. mDNS/DNS-SD is known in Apple circles as “Bounjour” and is part of the Zeroconf suite of protocols.