I used to fill out hundreds of pdf application for my clients, but then I learned how to use API and connected my spreadsheet to prefillpdf api, so now everytime when i have new client i just add data to my google sheet, it reads it and then builds pdf and saves it in google drive.
That looks like a nice workflow and seems really neat and interesting. However I am curious how exactly you are adding the new from the PDF to the GSheets, I see you are updating the file in GDrive but I am curious where you are actually manipulating the data with the new information?