We have a wired connection in the house and some devices automatically select it (wirelessly). However the printer is on a wireless connection and doesn't 'see' the wireless devices. Can a device be forced to use a wireless rather than the wired connection?
What do you mean when you say "We have a wired connection in the house and some devices automatically select it (wirelessly)".
Do you have the printer connected by Ethernet and wireless. If so and you just want it to use the wireless signal you would need to remove the Ethernet cable.
Your printer won't "see" the wireless devices, it will only see the device that is broadcasting the wireless signal, ie your router/homehub.