So, I think it's definitely possible to generate a bill of sale for your transactions through PayPal. I mean, PayPal is widely used for buying and selling items, and it's generally a secure platform.

I suggest looking into PayPal's invoicing feature which allows you to create and send detailed invoices to your buyers. That way, you'll have a record of the sale and it'll be easier for you to manage your transactions. I hope that helps!