I have PDF form hosted on a local server

I created a web page where this form is embedded via iFrame

I have a submit button on that page said page

What I need to figure out:

If submitBtn is clicked > save the PDF with the user's changes to a predetermined location on our network with a unique name (could be a simple numeric iteration) > generate a link to that file for the user to copy

If this possible? I'm very new to JS.

Thanks!