Magento Open Source 2.1.x
PayPal Payflow Pro

PayPal Payflow Pro gatewayA transaction bridge between a customer and a payment processing service that is used to transfer money between the customer and the merchant., formerly known as Verisign, is available for customers of the United States, Canada, Australia, and New Zealand. Unlike other PayPal payment methods, merchants are charged a fixed monthly fee, plus a fixed fee for each transaction, regardless of their number.

Setting Up PayPal Payflow Pro