The Affiliates manager plugin can be integrated with the Gravity Forms PayPal addon so that affiliate commission is given to the affiliates that send visitors to your store/site.
Step 1 (Install the Plugin)
Install and activate the Affiliates Manager Gravity Forms PayPal Integration addon
Step 2 (Keep the Main Plugins Active)
Simply keep Affiliates Manager, Gravity Forms and Gravity Forms PayPal addon active on your WordPress site.
When you receive a PayPal or PayPal Pro order in the Gravity Forms plugin, the affiliate plugin will award commission to the appropriate affiliate (if the customer was referred by an affiliate).