Have a look at this article...

View PDF files using Firefox’s built-in viewer

...and let us know if it helped

Note that "Viewing PDF files in Firefox without downloading them" is misleading. What is meant is that you aren't downloading and saving this file directly to a folder on your computer. Firefox will have to download the PDF file to be able to display it, but may keep the file in the memory or disk cache.

Current Firefox versions have enabled a built-in PDF Viewer that doesn't have all features that other PDF readers like the Adobe Reader have or may not function properly otherwise.

You can change the action for Portable Document Format (PDF) from Preview in Firefox to use another application like the Adobe Reader or set to Always Ask in "Firefox > Options/Preferences > Applications".

You can set the pdfjs.disabled pref to true on the about:config page to disable the build-in PDF viewer.

You can check the value of the plugin.disable_full_page_plugin_for_types pref on the about:config page and remove the application/pdf part if present or reset the pref to the default via the right-click context menu.

I have a similar problem. All my options are set to 'use Adobe Reader' but when I attempt to download a pdf file a new tab opens, 'connecting' displays for a few seconds but I am then left with a blank tab and no content displayed. Is there another problem and another solution?

Hi condonm

I assume that you changed the setting in Tools > Options > Applications to use the Adobe Reader.

Is that to use the AR plugin in Firefox or to openthe file in the external reader

Is the built-in PDF Viewer still enabled?

What are the values of these prefs on the about:config page?

• pdfjs.disabled
• plugin.disable_full_page_plugin_for_types

Thank you cor-el. Yes I did change settings in Tools>Options>Change to use adobe reader in external format. PDF viwere is enabled.

Where do I find about:config page?

You can open built-in about: pages via the location bar like you open a web page.

• http://kb.mozillazine.org/about:config

Thanks for your very rapid responses! I had installed Nitro download plug in 3.0.0.2. The trial period had expired and it was blocking normal function. Deletion of the plug-in has solved the problem.

Many thanks all the same. It all adds to the reservoir of knowledge.

Thank You For Your Replies And Solution. I used DocuCom pdf plus plugin in previous Firefox Version. But Now I Can't Install That Plugin. I Think It's Better Than Other.

I don't know if this is any help I have had a problem where the pdf files were not opening correctly which I think was the problem here. I spent hours of head scratching and have now found out what the problem is. Right click on the Adobe Reader Icon on the desktop. Select properties and then the compatibility tab. You will see the uppermost section in this screen is Compatibility mode. I have Windows 7 and mine was set to Windows XP. I changed that to Windows 7 and now the problem is resolved. In short use the above instructions to check you are using the right compatibility mode for the version of Windows you are using and your troubles should be over!!

This PDF Document Viewer is often applied to assist in PDF document viewing, reading, processing, scanning and manipulating. It can be used for viewing and reading PDF document in ASP.NET web, .NET Windows Forms and mobile developing applications.

Same problem. Am using Firefox 24 (W7x64).

I've tried setting it to use the built-in PDF viewer, to always asking, to using Adobe plugin, to using Nitro plugin.

I changed the pdfjs.disabled in about:config to true but that didn't help.

The plugin.disable_full_page_plugin_for_types was set to user set string ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

I changed it to default, string but that didn't help either.

The pdfjs.database is set to {"files":[{"fingerprint":"a217d02eee11bdca6fa87ec7d192fd7","exists":true,"page":1,"zoom":"auto","scrollLeft":0,"scrollTop":800},{"fingerprint":"2fc235a8bd85f838d74c927cfcd9842","exists":true,"page":2,"zoom":"auto","scrollLeft":0,"scrollTop":587},{"fingerprint":"c839bb8d692bce1ea48d681a35741e49","exists":true,"page":1,"zoom":"auto","scrollLeft":0,"scrollTop":792},{"fingerprint":"3dc145587d24022921d7e241bc3a5","exists":true,"page":35,"zoom":80,"scrollLeft":360,"scrollTop":707},{"fingerprint":"18a76da679de944893795ed1e4a136","exists":true,"page":2,"zoom":110.00000000000001,"scrollLeft":0,"scrollTop":662},{"fingerprint":"d8270f838618eeca6ea969e255b239f","exists":true,"page":24,"zoom":"auto","scrollLeft":0,"scrollTop":51},{"fingerprint":"443a32303133303630333137313132342d303427303027","exists":true,"page":1,"zoom":"auto","scrollLeft":0,"scrollTop":772},{"fingerprint":"443a32303133303631303135343033332d303427303027","exists":true,"page":1,"zoom":"auto","scrollLeft":0,"scrollTop":772},{"fingerprint":"443a32303133303631303132323731332d303427303027","exists":true,"page":1,"zoom":"auto","scrollLeft":0,"scrollTop":772},{"fingerprint":"443a32303133303631373133313733372d303427303027","exists":true,"page":1,"zoom":150,"scrollLeft":0,"scrollTop":772},{"fingerprint":"591aede8aeea4ade9612674263eaf4a2","exists":true,"page":1,"zoom":"auto","scrollLeft":0,"scrollTop":772},{"fingerprint":"443a32303133303830353132353132372d303427303027","exists":true,"page":1,"zoom":"auto","scrollLeft":0,"scrollTop":772},{"fingerprint":"8bf283ba7a5cc5479db8405215d67d3","exists":true,"page":1,"zoom":"auto","scrollLeft":0,"scrollTop":1008},{"fingerprint":"768e8216a07384f961d92204d6a1ef8","exists":true,"page":1,"zoom":"auto","scrollLeft":0,"scrollTop":800},{"fingerprint":"a4649ba52b2dcd144b35b9bd5c10a7","exists":true,"page":52,"zoom":"auto","scrollLeft":0,"scrollTop":290},{"fingerprint":"d612d5d934c66f4aa936b5b0a6cce91","exists":true,"page":18,"zoom":"auto","scrollLeft":0,"scrollTop":168},{"fingerprint":"de55bb394d87ed4cb8dd7584c4b68f61","exists":true,"page":1,"zoom":"auto","scrollLeft":0,"scrollTop":612},{"fingerprint":"fd4b802248d8a94e825747cf2ba32e2f","exists":true,"page":4,"zoom":"auto","scrollLeft":0,"scrollTop":109},{"fingerprint":"229e846140d9925da79a11f7d6cae","exists":true,"page":1,"zoom":"auto","scrollLeft":0,"scrollTop":800}]}

I'm not convinced by the presence of this pdfjs.database pref of whether there is a maximum number of entries to remember which PDF files you have viewed as this looks like a privacy issue to me if history is kept in the prefs.js file.

Just trying to find something that could explain why I can't open pdf files in Firefox. Having to switch to Chrome everytime I need to do that is a real pain.