Add Signature to PDF via the API

Hey Community, 

I am reviewing the Adobe Sign api, and can not find a specific end point for what I want to accomplish. 

I am using a form tool specifically to gather user data, when they complete the form from the tool I am using, I want to make an api call specifically to apply a signture of the user that filled out the form to my pdf through the API and I was wondering how to do that? 

Anything helps, if you have python examples of this even better!

Thank you!