Shipping to PR can be done by Deta Dash and the only paperwork requiered is a Health Certificate for the animals.
The only thing you have to be carefull is that only BP's and Garter Snakes are legal here so no other snakes can be shipped.
You can also use FedEx or UPS but they always complain about shipping reptiles to PR and they always ends by telling you no, but thats only becasue they don't want to take the time to look what is legal here or not.
You can contact Raul from West Coast Jungle, he take the time to get Delta Dash Certified and get the Health Certificates to ship a few BP's to me last year.