Request:
A Microsoft Word document can be either a .docx or .dotx, the difference is that when saving the .docx, the file is overwritten; when saving the .dotx, a new file is created. I propose a similar feature for PDFs.

Use Case:
I've created a fillable PDF and saved it as a PDF to a network share and SharePoint. People have the tendency to open it, fill it out (as they should) and then click save (or Ctrl-S, muscle memory). That commits those filled form fields to the file system such that the next person who opens the file now sees a filled-out form.

I would like to do something to the file so that "Save" doesn't work. For example, if the file extension were .pdft, and I opened it, it could behave the same as any other .pdf. However, when I chose to save the file, a compliant program would recognize that the preference is to create a new file, not overwrite the existing file.

Context:
I propose a file extension change instead of metadata in the file because it is much easier, and doesn't require the PDF standards consortium to get involved. A non-compliant program would just overwrite the file as usual. This means that any PDF program could open a .pdft file simply by, in Windows, right-click, open with, and choosing whatever program; they would see no functional difference. However, a compliant program would make the default save operation require a new file name.

Such a convention would also be very easy for PDF tools made by other companies to implement more quickly promoting this convention.

This has been asked of the Adobe Community before: https://community.adobe.com/t5/acrobat-discussions/can-i-create-a-pdf-quot-template-quot-akin-to-word-s-template-dotx-function/m-p/10485536