Updating adobe reader
After the Adobe Reader download is finished, close your Mozilla browser, go to the location where you saved the installation file (e.g., your Desktop or Downloads folder) and then run the installer.
Alternately, review the Adobe Reader system requirements, go to the Adobe Reader FTP site and download the installer for your operating system and language.
When I tested it in a collection with 4 computers it was successfully deployed, so I pushed it out to the rest of the network.
Within minutes I had multiple help desk calls regarding Adobe Reader disappearing from computers.
See this Firefox Support article and bug 714712 for details.