If you allocate 100GB to Windows, 200GB to Pop and 200 GB to Fedora (or another distro) you will still be able to boot on pop and retain those documents while having an entirely different OS (fedora) from which you can boot with its own files and config which won’t impact your Pop.
If you’re more tech savvy you can even create a share partition on which you can store files that are easily transferrable between these 3 OS.