PDI= Pre Delivery Inspection. When you go to pickup your unit, you want to do a PDI. It will usually take 2--4 hours. You need to have tech show you how to operate, open, close, turn on, turn off, run slides in and out, test everything. Water, A/C, all electrical, televisions, anything and everything needs to be tested.
Some people, most I think, do not sign final papers until PDI is complete and any adjustments or repairs are done to their satisfaction.
You will get more info from our other members also.
Jim M