You can easily prefill a document by saving the document who needs to sign as 'Me & others'.
Even if you don't have to actually sign the document, you can still designate text fields to yourself.
Just make sure that you set yourself (sender) as 0 and the recipient (contact 1) as 1. The moment you click sign and send you will immediately be prompted to fill in the text fields that you would like to be pre-filled.
The video below will also explain how you can pre-fill a document.