I am trying to find the best way to accomplish this and hope that there are some open source solutions that exist. I currently have a form that will accept a user's API key and file. When given the API key and file selected, it will upload the file to their user account. They can then download the file from the website.
I am looking for a way to have a Virtual Printer that will store the user's API key and allow them to be in whatever program on their computer. When they have finished making changes to their file, they can "Print" using a virtual printer to the website's API.