They're not PADS, they're SHOES. They work like a small drum brake, with the "drum" being the cylindrical section of the rear rotors. To help you imagine this, you would see some sections of the parking brake mechanism by looking in the holes the wheel bolt screw into. I wouldn't mess with it without some training, it can easily be screwed up. The shoes themselves are adjusted with star wheel adjusters through one of the wheel bolt holes, but there is also an adjuster on the parking brake equalizer.
To adjust it correctly, the equalizer adjuster is slackened, then the star adjusters tightened fully and then loosened a predetermined number of teeth (sorry, I don't remember what the number of teeth are for a 129, I think it's 6 to 8 teeth), then the equalizer is adjusted to remove cable slack, and the number of clicks the pedal can be depressed is measured, and the cable can be further adjusted based on the number of clicks you get.