Forms you create with the Gravity Forms Plugin can have PayPal links. 

To edit the settings, go to Forms, hover below a form, then the Settings option of the tools that appear, and click on PayPal.

Click Edit below a PayPal feed, or Add New to create a new PayPal feed.

This takes you to the Feed Settings screen, where you can name the feed, connect it to an Email that has an associated PayPal account, and manage other features.