PDF fields and automation

Good afternoon!

I am in need of guidance from the community on which package/products to purchase to get to my end goal. I am converting contracts to pdfs. I would like to have those contracts have fields that can be populated from a text file with fields of like names. Simple example; basic contract with first_name, last_name, address_1, address_2, city, state, zip and be able to use python or something else t populate those fields from a separate file. I have the python side worked, just not sure what all I need on the pdf side to make this happen. Help!!