Paypal has multiple website pages that promise a full refund, including original shipping. But caveat emptor!
One of the caveats, hidden deep in the bowels of their legalhub is quote "if you're filing a Significantly Not as Described claim. PayPal may require you, at your expense, to ship the item back to the seller, to PayPal or to a third party (which will be specified by PayPal) and to provide proof of delivery." WHAT THAT MEANS TO YOU IS "if the merchant makes a mistake and sends the wrong thing, the consumer is responsible for covering the costs of that mistake."
But wait! It gets worse. The merchant I purchased from posts a return policy specifying that the consumer is not responsible for return shipping when the wrong item was sent. I ordered a black shirt and received a white shirt. Despite the merchant's return policy, PayPal refuses to process a refund until I send the white shirt back AT MY EXPENSE.
So, before purchasing something from a PayPal merchant, consider how much it's going to cost you to send it back if the merchant sends the wrong thing.