Finally, a fix for the PDF preview bug in 64-bit Windows

Way back in May 2008, I noted an annoying, longstanding bug that surfaces when you install Adobe Reader on Windows Vista x64. The preview function, both in Windows Explorer and in Outlook 2007, is broken. The only fix I could find at the time was to replace the broken previewer with a third-party alternative such as FoxIt PDF Preview Handler.

Now, 16 months later, there’s a new 64-bit operating system, Windows 7, and a new version of Acrobat Reader (9.1). And the bug is still there. Here’s what you see if you try to preview a PDF file in Windows Explorer under Windows 7 x64:


But yesterday, Leo Davidson pinged me via e-mail with news that he had discovered the cause and, more importantly, had a fix for it. As Leo notes, the problem is caused because Adobe registers the wrong preview handler, even though Microsoft explicitly documents the correct settings, The fix involves replacing the incorrect registry value with the proper one.

If you are running a 64-bit Windows version and you’ve experienced this issue, you can edit the registry by hand, using Leo’s step-by-step instructions. An easier fix is to create a Registration Entries file (.reg extension) that makes the changes automatically when you double-click it. You’ll find a downloadable version of this fix-it file at Leo’s site as well, just above the instructions for manually editing the registry. Download and unzip the adobe_pdf_x64_fix.reg file and follow the prompts.

As I discovered during my tests, this fix requires one extra step if you’ve previously installed the FoxIt Preview Handler. Open Control Panel, double-click the entry in Programs and Features for Adobe Reader, and run a Repair installation. After you complete that preliminary step, the fix should work just fine. Here’s what the preview pane looks like when it’s working properly:


As Leo notes, it would be nice if Adobe would fix this bug. (Actually, he’s a bit more forceful than that, and he’s right. Hey, Adobe, fix it!) It would be trivially easy to do so, and they could win some friends by getting it right with the next release of Reader.

31 thoughts on “Finally, a fix for the PDF preview bug in 64-bit Windows

  1. Well that’s great and all, but what about the thumbnails?

    Fear not, i have the answer.
    PDFXchange 64 bit will bring you full thumbnails in Vista/7 64 bit.

  2. Amazing that a problem with such a simple fix could be ignored by Adobe for so long. It’s like they’re wilfully ignoring x64 as a platform – I can’t think of any other excuse for this issue being unaddressed after all this time.

  3. I think, perhaps, Adobe is errant because MS is stealing its thunder with Silverlight. Could it be just that simple?

  4. I find Foxit reader to be better overall than Adobe Reader… I haven’t used Adobe Reader in ages, and judging from this post, I didn’t miss on much 🙂

  5. I find FoxIt’s text rendering harder to read than Adobe’s.

    The banner advertising the fact that FoxIt is being used in the FoxIt preview handler also has no place on any monitor of mine. 🙂

    Adobe Reader 9 starts very quickly (much improved over previous versions) and the preview handler in question starts even quicker.

    I’m no fan of Adobe, and have a lot of my time wasted working around the various bugs in their PDF software over the years, but as a user Adobe Reader 9 seems okay to me. I get the impression many use FoxIt instead because of reasons that no longer exist. Still, if you prefer it then more power to you!

  6. No, I don’t think it’s that simple, Bill. The problems with Adobe Reader go back ages, to a period long before Silverlight was even a possibility.

  7. Just wanted to extend my gratitude to Leo, for making this fix (easy or not – I didn’t have it before) and to you Ed for making me aware of it. The fix works in Outlook 2010 Technical Preview as well. 😀

  8. AboKevin, are you running 32-bit Office 2010 or 64-bit? I haven’t been able to get PDF previews to work in 64-bit Outlook 14 (Office 2010) but assume that’s because the previewer is 32-bit and won’t work with a 64-bit app. Can you confirm your configuration?

  9. Ed, I must admit that I couldn’t answer your question straight up without some checking. I found that I have downloaded both x86 and x64 versions from Connect. Checking my C drive I found that most of the Office files are in the Program Files (x86) folder, so I assume I have the 32-bit version of Outlook 14 installed on my 64-bit Windows 7 Ultimate system. Why I did that beats me…

  10. OK, that explains it. Btw, an easier way to check is to run one of the programs and then look at the Processes tab in Task Manager. If it’s a 32-bit process you’ll see *32 at the end of the associated process.

  11. It should be able to work from a 64-bit process since it works from 64-bit Windows Explorer as well as the 64-bit version of my own viewer.

    The fixed AppID registry setting should mean that a 32-bit copy of PrevHost.exe (“Preview Handler Surrogate Host”) is created to host the 32-bit Adobe PDF DLL. PrevHost.exe then acts as a proxy between the 32-bit DLL and the main 64-bit process. COM magic. 🙂

    (The problem before the fix was that Adobe set the AppID to point to the 64-bit PrevHost.exe when installing on 64-bit systems. The fix changes it to the 32-bit PrevHost.exe, as is required for hosting a 32-bit DLL.)

    It’s possible that Office 2010 is loading the viewer in a way which prevents PrevHost.exe from being used. I don’t know exactly what Explorer does but in my own code I explicitly check for 32-bit viewers and do things a little differently for them. Maybe that’s why it’s working for me (and Explorer) but not Office 2010. I those extra steps were redundant for preview handlers — they are in my code for other types of ActiveX control — but maybe not.

    I also had to change my code slightly due to changes between Vista and Windows 7 in the way 32-bit and 64-bit preview handlers are listed in the registry. (There used to be separate lists for 32-bit and 64-bit. In Windows 7 there are still two lists but they both contain a merged list of all the viewers irrespective of their bitness.) Could be that affects Office 2010 as well.

    These are all guesses, though. It could be something wildly different.

  12. Hmm. For some reason, this fix has not worked for me. I still have the “This file can’t be previewed… blah blah” error message displayed in Explorer.exe for PDF previews. I’m running Win7 x64 final. Acrobat 9.1.3 from Adobe CS4.

  13. Ed, yes I had tried uninstalling/reinstalling Adobe Reader 9.1. Actually I did figure out the issue, hopefully this will help some others:

    in the .reg file, the fix is applied to the WOW6432 node of the registry ONLY, which is not correct. Actually there are 2 locations that need to be patched:

    Windows Registry Editor Version 5.00



    Once these are both entered, the previews work fine!

  14. I’m still looking for icon view fixes for both PDF and Office files. These often break both in 64-bit and 32-bit Windows. Fixing them is not always a piece of cake, if it can be done at all. Very frustrating!

  15. @Freudslipped

    Explain to me how x64 is the ugly stepchild of MS when what we are discussing is how Adobe still haven’t fixed a relatively small and easy bug in their software? Your logic is impeccable… or not…

  16. The “fix” for thumbnails in Vista x64 is to launch the 32-bit version of explorer.exe, by making a shortcut that points to:

    C:\Windows\SysWOW64\explorer.exe /separate

    Then view in thumbnails works. Sadly, it looks like MS has “shimmed” this in Win7 and the shortcut launches a 32bit app but it gets swapped out almost instantly for the 64-bit flavor. So this trick no longer works in Win7. I even tried taking the 32bit explorer.exe file from my Vista SP2 x64 and running it in Win7 but it refuses to launch. I wonder if there is a 32bit explorer.exe from Win2008 server that might run in Win7, I haven’t had a chance to test that yet.

    So… hopefully Adobe will get their act together one of these YEARS and release a “real” compatible version of Acrobat for x64. I tried the available 3rd party solution (PDFXChange) and found it to be quite buggy (I got black squares for a lot of my thumbnails, and they were hit-and-miss).

  17. Luke:

    On a 64-bit system


    should not exist at all.

    Either you had run the 32-bit version of RegEdit (which would happen if you launched RegEdit.exe from a 32-bit program, e.g. 32-bit Explorer) or something weird is going on.

  18. Luke: Did you do an upgrade install from Vista 64-bit to Win 7 64-bit? That could explain why the CLSID is in the 64-bit part of the registry.

    (Though my reading of the rules says it still shouldn’t be there, even then, it could explain why it’s different between our machines. Mine’s a clean-install.)

  19. @AboKevin

    You seem to be of the opinion that my query is illogical or possibly a Microsoft bash.

    I am of the opinion that Microsoft’s OS x64 is more stable and better performing than the alternative. In fact, it continues to be a great product. My belief is that the failure of third party hardware and software developers to produce a wide range of viable products for x64 is directly related to the lack of emphasis placed on the OS by Microsoft.

    To put it short and sweet: Adobe would have fixed this bug a long time ago if x64 had a greater market share. x64 isn’t going to have a larger piece of the pie until Microsoft decides to get behind the future of stable computing; x64. This leads to my view of x64 being treated as the ugly stepchild.

  20. @Leo Davidson:

    Yes, I did do an upgrade from Vista x64 to Win7 x64. Hmm. I wonder what other problems this might have caused. Guess at some point a ‘clean install’ is in order. But for now, everything is working fine.

  21. I’m surprised a Windows guru is recommending the use of Adobe Reader when there are far better options out there.

  22. Ocean, where did I “recommend Adobe Reader”? Some people like it and use it. Some people are required to use it for work because of licensing reasons. I don’t pass judgment on their decision. Neither does Leo. My goal is to help, not to preach.

  23. I too had to change both [HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Classes\CLSID\ and
    [HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\ to get this to work.

    Note: My system was an in-place update from Vista to Win7 RTM 64-bit.

    Thanks Luke H!

  24. Thanks Luke H and John-D! I’ve added a note about that to my page in case it helps others.

    As for x64 itself, I think it will inevitably increase in market share now that mainstream machines are being sold with 4+ gig of RAM and after Vista x64 paved the way by proving that x64 was a stable platform with very few issues (stuff like this being one of the issues, of course).

    I know I didn’t have the guts to switch to x64 when Vista was new but it’s a complete no-brainer now. MS still have to keep an x86 Windows version for hardware that requires it (e.g. Intel Atom netbooks) so I don’t blame them for that. It’s now in the OEM’s hands to do the sensible thing and ship x64 by default on hardware that can run it.

    I’ve had x64 on my Vista laptop for 9 months and on my Win7 desktop for 1.5 months and I am rarely conscious of the fact it’s not 32-bit, which is how it should be! 64-bit Windows is a success.

    Regarding FoxIt vs Adobe Reader, I don’t mind what anyone uses. To be honest, if I had my way I would never have to view another PDF (or .DOC or .XPS or…) on my computer again. Viewing digital sheets of paper on-screen, with their page-breaks, headers, footers, unsuitable fonts/layouts for monitors, etc. etc., was never my ideal for the “paperless office.” 🙂

  25. I changed [HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Classes\CLSID\ and imported
    [HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\ but still can’t get it to work

    Note: My system is a Clean instal of Win7 RC 64-bit.

  26. Ed:

    Your fix also works for the full version of Adobe Acrobat 9 Pro. I wish that someone could figure out how to get pdf thumbnail previews to work on Win7 x64. There is hope because I’ve noticed that if you choose “File Open” while running Acrobat 9, the dialog box that opens will cause a thumbnail preview to be generated, which persists when you view the file with Windows Explorer.

    This “trick” doesn’t quite do the right thing because the thumbnail doesn’t resize when you change the view size in Windows Explorer. The thumbnail preview is only present at the size that was in use when the preview was generated. At other view sizes it reverts to the Adobe icon.

  27. Well, you really can’t expect Adobe to pay attention to details that impact the functionality (or security) of their products.

    Not when they are spending so much time figuring out new ways to foist useless/unwanted garbage like Adobe Air, and the spectacularly horrible Adobe Download Manager (as well as any number of third party toolbars and applications) on us.

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