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I can no longer open .pdf files in Firefox 4

  • 35 replies
  • 2485 have this problem
  • 1972 views
  • Last reply by sdhaliwal63

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Ever since I moved to the beta version of Firefox 4, I have lost the ability to view .pdf files in Firefox. I was convinced this was a problem totally with Firefox, but at around the same time I upgraded from an old G4 PPC laptop to a new Macbook Pro. Now I find I can't view .pdf files in Safari either. Is this a problem with Firefox, or a problem with the way I have configured my new computer?

All Replies (20)

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I started having the same problem when I downloaded Firefox 4 beta and continue to have the same problem with the non-beta version. However, the pdf links work fine in Safari for windows and IE, so the problem must be with Firefox. I'm about to go back to an older version.

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I did have an issue with a PDF at one point, but it only seemed to be on one site, so I promptly forgot about it (and put it down to a bad file) - anyone got a site link of a broken PDF situation I can point my browser at to test?

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Opening PDF-Files is a function usually provided by a seperate application (like Adobe Acrobat) through a plug-in. Have you tried to reinstall you current PDF-Application? When you click Firefox (upper left corner) -> Add-ons and click on "Plugins" on the left side, do you see your PDF-application displayed there (e.g. Adobe Acrobat)?

Modified by Janzomaster

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When I went Firefox 4 beta, the plug-in I was using was not compatible. I recently found a compatible plug-in; unfortunately it runs in 32-bit, and my 1Password plug-in only runs in 64-bit, so I have to choose until a compatible 64-bit PDF viewer plug-in becomes available. Thanks for the advice!

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I managed to get the Adobe Reader plugin working by following the instructions found on the PluginDoc link, which can be found at the bottom of the Plugins page.

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We are no stupids, pdf viewer is a plug-in of Firefox, (Firefox pdf plugin), but in FF4 it doesn't work. However, it's incredible that Firefox doesn't include a pdf viewer by default. You don't need to save every pdf that you want to see in the web.

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I have the same problem and I agree with firebunny. This is really bad style from Mozilla. You should have thought about a problem such as viewing pdf's in the browser and compatible pdf-reader plug-ins.

My Adobe Acrobat plug-in was disabled by default when I installed FF 4 rendering viewing and downloading pdf's impossible. Now I am stuck with this browser and am considering going back to the last 3.6.16 version that I still use at my workplace without any problem.

Also I agree that this has nothing to do with the pdf readers that should be installed on the PC but with FF 4. I can prove this since I installed foxit-reader which also comes with a FF compatible plug-in. Neither here did selecting this as the default pdf application help nor does it enable downloads.

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I too had the same problem, however the solution turned out to be real simple. Simply first close Firefox, then re-install the most current version of Adobe Reader (Vers. 10.0.1), and re-open FF. All is working well for me in that department

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Finally I manage to solve the problem. The instructions on [page] helped me, but they are not up to date.


  1. You have to find nppdf32.dll in your adobe acrobat folder.
  2. Then copy the file to C:\Program Files\Mozilla Firefox\plugins.
  3. Problem: the folder doesn't exist in the new Firefox.
  4. Solution: create the folder.
  5. Everything should work after a restart of Firefox.

I just don't understand why there is no longer this \plugins folder and why the plugins are scattered everywhere.

Modified by plophy

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Screw this! Went back to FF 3.6.16 and viewing and downloading pdf's now works like a charm again. That goes for Adobe Acrobat as well as Foxit Reader.

When you have finished testing your FF 4 beta let me know and I'll move on to it once all the flaws and errors are corrected.

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Disabling PDF Download fixed it for me.

I have used PDF Download for a number of years, currently version 3.0.0.2 is installed. I to could not open any PDFs (only the odd direct link), I disabled PDF Download and I haven't been able to find a PDF that I could not open (even ones that are fetched with javascript).

This is a shame because I really liked PDF Download, I hope there is an update soon.

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RE: plophy's suggestion of copying the dll file to the FF folder...

This worked for me! However the plugins folder was already there in the Firefox folder. All I had to do was copy the dll file to the plugins folder and restart FF. Worked like a charm. THANK YOU!!!

Modified by MissTrish73

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I went into options in FF and changed the default pdf reader from Adobe Acrobat to Adobe Reader since it now costs for Acrobat, I think. Anyway I don't have Acrobat. The files download but at least I can read them now.

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If you have the PDF Download Add-on you must disable it. There appears to be a conflict with Acrobat. Also in Tools-Options-Applications assign Adobe Acrobat Documents to "Use Adobe Reader". You must do this if you want to save the file as a PDF. For some reason (?) if you use the "Use Adobe Acrobat" selection, Firefox saves the document as an htm page. Go figure?

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That hasn't been an issue. I have had Firefox set to open .pdf files in Acrobat and it works fine. I just prefer to read them directly in Firefox rather than having to flip back and forth from one app to another. I am able to safe .pdf files as .pdf files just fine in Acrobat.

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I have the nppdf32.dll file in C:\Program Files\Mozilla Firefox\plugins, but I still can't view PDFs.

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Hi Uninstall acrobat reader 10 and install acrobat reader X Worked for me.

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Hi Does any body file a defect for this issue? If Yes, Please post your reply.

Thanks Arshad

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I have the same problem when i install firefox 4.

To resolve the problem, i uninstall the module PDF Download and install the module gPDF.

Good Luck !

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