PayPal won't give you an overdraft. If your PayPal account doesn't have sufficient funds, it will use your primary source of funds to make the rest of the payment. If your primary source of funds is a credit card, it will use that. If your primary source of funds is a bank account, it will use that, and if your bank account doesn't have enough funds then - assuming you have overdraft arrangements - it will be overdrawn and you'll be charged whatever your bank charges for overdraft facilities.
But PayPal themselves are not involved in this. They just take the money from wherever you've told them to take it.
But PayPal themselves are not involved in this. They just take the money from wherever you've told them to take it.