| Great info in the pdf you attached dirty tool. Here's the message from a BMW tech that basically describes step one in layman's terms. Hope this helps in case adj the cables is not enough.
You'll want to remove both rear tires for this. Go to one side, it doesnt matter which one you go to first. Get yourself a flashlight or something. Kneel down and shine into your lugbolt holes(where the bolts for the wheels screw in). Pick one hole and stick with it.
Spin the rotor while looking in one of the holes till you see a silver gear looking wheel. It looks about the size of a penny with teeth going around it. When you spot it, get yourself a screwdriver and pry
up on the gear, making it spin. Spin it about 5 turns, then go to
the other wheel and do the same thing, but spin the other side the opposite direction. Do the other side about 5 turns as well and go pull your handbrake to see if it's any stiffer. If it's not, try turning that gear wheel on both sides the opposite way. Adjust till you get a firm hand brake lever.
This adjustment is a bitch if you havent tried it before. I would suggest taking it to a dealership. They'll probably charge you an hour to do it...which may run you from anywhere between 70 to 100 bucks.
If you don't want to take it to a dealership, try a known good independant shop. Too bad you probably don't live close to where I am, I'd help you out and do it for ya.
Let me go ahead and tell you, you're not going to "mess anything up"
here. The most you could do it loose all your parking brake, which
has no correlation to your regular brakes. I hope this helps a
little. Like I said, this is a hard adjustment to describe here in email. Hope this helped a bit.
Let me know what happens... | 
