I think it is going to come down to “how badly do you want this file?” There is a Windows program called iExplorer that supposedly can pull files off an iOS device, but I haven’t used it and can’t vouch for it other than to say it exists. It costs $40, by the way.
https://macroplant.com/iexplorer
I don’t know of any Apple-sanctioned (and free) way to transfer files from device to computer; that’s not the way Apple designed the system, unfortunately. The only free approach I can think of would be to set up a mainstream Linux system like Ubuntu and see what the current state of Linux support for iOS file transfer is. Typically iOS support lags behind on Linux, as Apple is continually changing the security model and underlying file structure with each iOS release, forcing developers to have to reverse engineer to keep up. If your iPad is running iOS 11 even this approach probably won’t work.