Replace pads if:
Surface of any given mounting bolt is not at least 3/32" below the surface of the pad. There is any de-lamination of the pad from the backing plate. There is any scarring, chunking, or missing pad material constituting a total combined loss of surface area greater than 3 square inches per pad. There is any single scar, chunk, or missing pad material that is greater than 1 square inch per pad.
Replacement pads can be found https://kenco.com/store/#pads