I was looking at the wiki page on printing. Aren’t cups-pk-helper and python-pycups either also required or at lease desirable?
What for?
i do not see a default usb local setup would need it.
I think it does as mine is usb and i installed cups then cups-pk-helper, python-pycups and system-config-printer. Then i installed the printer driver from the AUR. It all sets up automatically and works. This is on a Canon MG2525. I tried before and it wouldn’t work without these. At least i couldn’t get it to work without those. 
cups-pk-helper is a optional dependency of python-pycups
python-pycups is dependency of system-config-printer (so it is installed)
Arch Wiki say:
Allowing admin authentication through PolicyKit
PolicyKit can be configured to allow users to configure printers using a GUI without the admin password.
Note: You may need to install cups-pk-helper for working this rules.
Just wondering if the Wiki should mention that cutps-pk-helper is optional and link ot the policy-kit reference that Joe mentions below
I don’t know. I just know that that is what i installed along with the other packages i mentioned and my printer worked. Maybe it’s not needed?