You have two versions of the Adobe PDF Reader plugin installed- v10 and v15. v10 is being loaded first, which is keeping v15 from loading. Type about:plugins in your address bar and press 'Enter.' Look for an entry which says "Adobe PDF Plug-In For Firefox and Netscape 10.1.13." Next, look at the 'path' entry a few lines above that. The path will look something like this: "C:\Program Files\Adobe\Reader\AIR\nxxdf32.dll" Next, close Firefox and then navigate to the location of the out of date plugin. Rename the plugin from example.dll to example.dll.bak. Now, re-open Firefox. The plugin page should no longer detect the old version of the plugin.