What all does the buyer need to bring with him so the title and registration on a trailer can get switched to him?

You need the original title, signed on the back by the same name as the owner on the front. If this can be signed in front of a notary, it makes life easier. You will need a bill of sale, stating the specific trailer (ser#), the price it was sold for, and again signed by the owner. You will need a current motor vehicle owner's card and proof of insurance. You will need a few checks, one to Penn DOT for the title and plates, one for sales tax on the selling price, and one to whomever processed your transfer.

If the trailer is an out of state arrival, it will have to be taken to an inspection station, where the ser # and specifics are verified. This will necessitate an additional form.

I belong to AAA and they have been able to transfer ownership relatively easily.