A Pennsylvania vehicle bill of sale is a legal document formalizing the sale and purchase of a motor vehicle between a buyer and seller. When selling a vehicle, the seller must sign and handprint their name on the proof of ownership document.Follow our comprehensive guide on how to make a legally binding Pennsylvania purchase agreement using our customizable template. A bill of sale is recommended if you're buying a motor vehicle, boat, or livestock. When buying a vehicle or equipment for your business, use this Vehicle and Equipment Purchase Agreement to protect yourself from unwarranted liabilities. Step 1 – Fill Out the Buyer and Seller Information. 1. Seller. Write down the seller's full name. The Pennsylvania bill of sale form acknowledges the transfer of possession of a piece of personal property for an agreedupon sum of money.