Most of the times after the release of a new Firefox version, add-ons may become incompatible. It's up to the developer to address these issues and update it accordingly. You can contact the developer from their add-ons page.

If you want to go back to a previous version, completely feel free to use the old, unsupported, and insecure versions of Firefox. Please remember that this puts your machine and personal data at an increased risk. You may then wish to mitigate that by having well rehearsed bare metal restore strategies or using a virtual machine.

I am doing my best to get Adobe to update the add-on. https://forums.adobe.com/message/6366189#6366189

And yes, I do a full backup daily with Acronis True Image and keep nonstop backup running.

I think Adobe wants you to upgrade to Acrobat XI... The new Create PDF 2.0 extension seems to be working without complaint (Firefox 29.0.1).

Does 1.2 display an error message, or just spin forever, or is it disabled? What exactly is going wrong?

Meanwhile, as a workaround, you might be able to get by printing to the Adobe PDF "printer" (no live links, subject to print-specific style sheets).

Adobe typically keep current Acrobat Pro version and previous version working (at least for security updates). I have submitted a request to Adobe (see above URL) but I am afraid you are correct.

The workaround is to click "View This Page in IE" (where it still works). I prefer Firefox and would much rather work there. I'll wait to see what Adobe do, but meanwhile I'll use IE for create PDF and install Firefox 29.0.1. It's not a good idea to use outdated Firefox.

Sorry, the answer to you question is it spins forever. The add-on is active and there are no error messages.

There is another workaround that I am using. Firefox ESR 24.7.0 Still works with Create PDF 1.2. Wish you had suggested it, took me quite awhile to figure it out.

Didn't know, thanks for reporting it.