In reply to earlsdonwhu:
That has never happened to me in over 20 car hires at PMO. They can't add it if you refuse to sign for it.
In reply to the OP
I tend to use one of the car hire aggregators, recently auto Europe, and ended up with noleggio, who although much cheaper than the competition have been very fair. Avoid the off airport operators, it takes a long time transferring.