Set up printer connected to Time Capsule via USB and print without WiFi

Question

Is there any way to do this? We use a Time Capsule for daily backups, for both Mac and PCs, and have a printer that we would like to share between all of them. Before, we had the printer connected to a PC as this allowed both PCs and Macs to print to it, but of course the PC had to be on. For whatever reason, when we plugged the printer into a Mac, the PCs couldn't connect or print.
From what Apple has told me, I have two options:
1. Share the printer via WAN, which is not desirable, as any other office could then print to our printer.
2. Create a hidden, password-protected, wireless network. This causes problems for two reasons. Firstly, we are not permitted to "extend" the network, and by creating a wireless network and attaching it onto the ethernet network, we are basically doing that. Secondly, if we did create this wireless network, computers that connected to the network to be able to see the printer would then default to the wireless network for internet access, rather than the ethernet connection.
If I am misunderstanding something, or someone has an idea of how to password protect a printer connected to a Time Capsule without using wifi, I would greatly appreciate it.

Answer 1

Sharing via WAN through the Time Capsule, for whatever reason, is not password protected. Any computer in our building can see the printer, and use it. When we were sharing the printer through the PC / Bonjour, when setting up the printer on a new machine, a valid username and password from the connected PC was required.
I should add that the purpose of trying to share this via the Time Capsule, rather than the PC, is that the Time Capsule is always on, and we notice an increase in performance when the PCs are powered down regularly.