Recently my Windows 7 computer has lost the ability to download PDF files from the internet. Previously when I clicked on a link to a PDF file either a new browser window appeared to display the file or the “Save as” dialog was displayed to save the PDF file to the computer. Now whenever I click on such links the “Save as” dialog very briefly flashes on screen but no opportunity exists to save the file. Reinstalling Firefox has not resolved the problem. I also have another computer running Windows Vista with exactly the same configuration and does not have this problem. Additionally, the problem does not happen when using Internet Explorer.

Since the problem does not happen when using Internet Explorer it is likely that something has gone awry with the Adobe Reader plug-in within Firefox. Internet browsers cannot open PDF files themselves, but instead rely on an external program to assist with viewing the files. The most common program which can be used is Adobe Reader, although there are alternatives available. We will deal with the situation where you are using Adobe Reader since that is the most likely PDF reader that you would be using. Adobe Reader installs itself as a program on your computer, allowing you to double-click to open and view PDF files on the computer. Additionally, Adobe Reader installs a plug-in within the detected internet browsers on the computer (in your case, Internet Explorer and Firefox) which allows PDF files to be displayed within the browser window. In actual fact, a cut-down version of Adobe Reader is being launched within the internet browser window giving the impression that Firefox or Internet Explorer is opening the file, when in fact it has passed the file to the Adobe Reader plug-in which opens the file and displays itself within the browser window. As you can probably see, if something has gone wrong with the plug-in then it is possible the PDF files will no longer display correctly and have strange behaviour such as that currently being experienced.

The actual installation of Adobe Reader on the computer seems to be fine, as it works correctly when viewing PDF files within Internet Explorer. Additionally, you can verify that the Adobe Reader program is working by opening any saved PDF file on the computer and ensuring that Adobe Reader launches correctly to view the file. Therefore, the problem seems localised to the Firefox plug-in for Adobe Reader. In this situation the easiest method to fix the issue is to completely reinstall Adobe Reader. As the first step, using the Windows Control Panel uninstall Adobe Reader. Once this has completed using Firefox, visit the Adobe Reader download page: get.adobe.com/reader . Follow through the prompts to download the latest version of Adobe Reader onto the computer. Once the installation has finished, restart Firefox and then check whether you are able to correctly view PDF files from links on web pages. It would also be advisable to check that Internet Explorer is still working correctly to ensure that the PDF viewing has not been broken in that browser as a result of the reinstallation.

Should the problem continue we need to check whether the Adobe Reader plug-in for Firefox has correctly loaded and is running within the browser. In Firefox, go to the “Tools” menu > “Add-ons”. Select the “Plugins” tab and you should see the “Adobe Reader” (or like) plugin listed. Ensure that the plug-in is enabled.

If the plug-in is enabled then all the obvious settings should make the Adobe Reader plug-in work correctly, so it is looking increasingly likely that something related to Firefox is causing the problem rather than the Adobe Reader plug-in. Before proceeding any further with troubleshooting Firefox you should ensure that the latest version of Firefox is running on your computer – you can download the latest version of Firefox from www.mozilla.com/firefox. Assuming that you are running the latest version of Firefox, yet the problem continues, the most likely cause is some other plug-in or add-on in Firefox conflicting with the Adobe Reader plug-in. We can test this theory by disabling all other plug-ins which are installed in Firefox and then check whether the Adobe Reader issue continues. In Firefox, return to the “Tools” menu > “Add-ons”. Select the “Plugins” tab and then select and click “Disable” to disable all the plug-ins except the Adobe Reader plug-in. Click “Extensions” and disable any installed extensions. Restart Firefox and check whether the problem still occurs. If not, one of those other plug-ins or extensions were conflicting with the Adobe Reader plug-in. In this case it will be a process of elimination to determine the specific plug-in or extension (collectively called add-ons) causing the problem. I suggest that you re-enable each add-on one-by-one, restarting Firefox each time and checking whether the problem occurs. When the problem starts occurring again you know that the most recently enabled add-on is the cause of the problem. In this situation you can either leave that particular add-on disabled (if you don’t need the functionality which it provides) or this at least provides you with a starting point from which you can do some research into how the problem can be fixed. Don’t forget that once you have found the problematic add-on you should also re-enable all the other add-ons which you disabled.

However, if you find that the Adobe Reader plug-in still does not work after disabling all of the add-ons then we need to look elsewhere for the root cause of the problem. Before proceeding any further ensure that you re-enable all of the plug-ins and extensions which you have disabled. Even though the Adobe Reader plug-in has been enabled within Firefox it is possible that the Firefox settings dictate that PDF files should be handled in a different manner and not use the Adobe Reader plug-in, or alternatively the Adobe Reader program, to open and view PDF files. In Firefox, go to the “Tools” menu > “Options”. In the Options window that appears, click the “Applications” tab. You should see several entries for “Adobe Acrobat Document”, “Adobe Reader Document”, or “Portable Document Format” (or variations on the above). Next to the type of file there is a drop-down box allowing you to select the action that should be taken when this type of file is encountered. If you wish to view the file within Firefox this should be set to “Use Adobe Reader (in Firefox)” with the plug-in icon. Alternatively, if you wish to view the file in the actual Adobe Reader then select the “Use Adobe Reader” with the actual program icon and this will open the files externally within the Adobe Reader program rather than within Firefox using the Adobe Reader plug-in. You can of course set other options such as “Save file” which will always save the file to your computer or “Always ask” which will ask you what you want to do. Just make sure that these are set to your preferred default behaviour so that Firefox does the correct thing when attempting to open the PDF files.

If the problem is ongoing after checking the default application behaviours for Adobe Reader then please contact me again for further advice as this is proving more troublesome to fix than expected. In the meantime, if you do need to view PDF files on that computer using Firefox, you can right-click on the link and select “Save Link As…” which will allow you to save the linked PDF file to your computer, which can then be double-clicked and opened within the Adobe Reader program on the computer. Of course, this is not a long-term solution since it is a rather cumbersome workaround (particularly if you view a lot of PDF files) but it should at least allow you to view PDF files while we are still working on getting this problem fixed.