Install and use Adobe Acrobat.
I already have it, that's what I'm using to try to edit. I tried uninstalling and reinstalling too. Thank you for trying to help though.
You must open the document in Adobe Acrobat, not Acrobat Reader.
This has caused a lot of confusion. I'm going to try to explain it.
There is an app called Acrobat Reader (or Adobe Reader). You have this app. There are a lot of buttons in it that invite you to buy. One type of button takes you to buy things like ExportPDF, a subscription. If you buy this, the Export button just works, right there in Reader.
But other things, confusingly, don't change Reader. The Edit button, for example, invites you to buy/subscribe to Acrobat Pro/Acrobat Standard (called just "Acrobat"). You can pay, but if you clicked the Edit button a hundred times it wouldn't ever change Reader and you'd always be asked to pay. The trick is that Acrobat Pro/Acrobat Standard are DIFFERENT APPS. You have to download it, install it, and use it. You will have BOTH apps, Reader and Acrobat; get to know which one is running and how to start the one you want.