how do i reinstall adobe acrobat xi pro

Hi … I am having trouble with my Adobe Acrobat XI Pro (v11.0.22) crashing after I scan a document. The problem is with Adobe as I have no problems when I scan using Paintshop. I have tried doing a repair installation, but that doesn’t fix the problem. If I reboot my PC Adobe is good for one document, and then on reusing the application it will start crashing again after scanning the first page of a document. I want to completely uninstall Adobe and then do a clean re-installation. How can I do this? I can’t find the registration or product serial number, I assume the registration was done using my email address and my Adobe ID sign in password. From where can I download the application software to do a new installation, and how do I preserve the registration I already have with my current Adobe installation. I am using Win10 Pro 64 bit. Can someone help me, please?