Perform the suggestions mentioned in the following articles: * [https://support.mozilla.com/en-US/kb/Template:clearCookiesCache/ Clear Cookies & Cache] * Update All your Firefox Plugins -> [https://www.mozilla.org/en-US/plugincheck/] ** '''When Downloading Plugins Update setup files, Remove Checkmark from Downloading other Optional Softwares with your Plugins (e.g. Toolbars, McAfee, Google Chrome, etc.)''' * [[Using the Adobe Reader plugin with Firefox]] * [[Opening PDF files within Firefox]] Check and tell if its working.

The above steps did not work for me. Internet Explorer 8 can open PDF files just fine so not sure why Firefox 10 is having issues.