Sorry for the problems that you're having.
Which Adobe product or service are you using? It's unlikely that you have "Acrobat 2.x" because that product came out in the mid-90s and no longer runs on any modern operating system. Can you double check which Adobe product or service you have, so we can best help you?
I am having the same problem. I have Windows 95 (still works like a charm along) and my Acobat v. 2.0.0 was working well but for some reason my Adobe AIR got corrupted so I had to download it. When I did, I got the same message that I had to upgrade to v. 2.3.0 and when I clicked on update, I get the same error message #16820.
[Moving this to Acrobat forum, as it's not related to CreatePDF.]
If you're looking for an update to Acrobat 2.x, this product is no longer supported. Our updates page goes back to Acrobat 3.x:
You can contact Support and find out if Acrobat 2.x updates are available, but I'm not sure they'll be able to find this.
Good day folks,
Unfortunately any updates for Acrobat 2.x are no longer available from the Adobe website. As Dave Stromfield mentioned, we still have updates available dating back to Acrobat 3.x (released in 1996), but nothing older. You may be able to locate the Acrobat Exchange 126.96.36.199 update in some corner of the internet, but we do not host those updates on our site anymore.
We apologize for the inconvenience.
Sorry for mis-diagnosing the issue the first time around. It sounds like the Acrobat.com Desktop Applicaiton is trying to update, not Adobe Acrobat 2.x. Unfortunately that update doesn't exist anymore and the Acrobat.com Desktop Application is no longer supported. I'd recommend uninstalling that application from your system. To access Acrobat.com moving forward, visit http://acrobat.com/signin.html