Adobe download only trys to tie into Explorer and fails at that. Mozilla does not seem to even be an option.
PDF web pages work on Explorer but not Mozilla. Went to the download link and downloaded. No options given as to browser. It seemed to pick the Explorer and tried to configure but even that did not work. Want it on my Mozilla as it is my preferred and default browser.
Wšykne wótegrona (1)
You have two different PDF reader plugins installed that Firefox can use, Fox-it and Adobe. Go into Tools > Addons > Plugins and disable the Fox-it plugin.
Also see this article and make sure Adobe Reader is set as the Action the PDF file types.
http://support.mozilla.com/en-US/kb/Managing+file+types