Getting Back Adobe to Use with Windows 8.1

Hello - I was planning to edit a Federal form I had saved on my computer.  I used to be able to edit any text or numbers a few months ago on it.  Now I think Adobe automatically substituted an older Adobe version I had with its latest version.  Apparently, I need Windows 10 or 11 to make it all work.  I have Windows 8.1.  I don't want to have to buy a Windows update, just for this one Adobe feature.  I am a basic computer user.  I don't want to buy a new computer, just for this Adobe update, too.  Is there anyway, I can get my old Adobe version back on my computer and no longet have the latest Adobe version on my computer to confuse things?  I'm not that computer savvy, so if anyone can guide me with simple instructions, so I don't screw things up, I'd very much appreciate your help.   Thanks