I'm using PayPal REST API to make calls using credit card numbers. So I have a form that requests credit card number to the users of the site. I could sell or use those credit card numbers that people insert.
So do I need any special permission (legal, whatever..) to have a form that request a credit card numbers?
How to feel users secure about inserting their credit card numbers on my website?
I'm living in Spain (Europe).
EDIT: I'm not speaking about storing the credit card number, I will not store the credit card numbers in a data base. I just use them for the calls to PayPal.
EDIT 2: maybe could be a good idea insert a PayPal iframe to my site? better than use PayPal REST API?