There does not seem to be any voltage on the pads where the LEDs would solder in. Is there a resister I need to stuff somewhere else?

A surface-mount resistor pack specifically, but yes.

I remember a post on this topic somewhere but could not find it.

There are several, but do a full-board search on "backlit buttons" to find Brian Mihulka's thread with pictures of his backlit buttons and knob.