I’ve ran into a few machines recently where users outlook no longer showing the preview for pdfs in outlook. (2010 and 2013) After searching it seems to be an issue with x64 bit versions of windows.
Preview handlers are lightweight components which let you view various file types within programs like Windows Explorer (in Windows Vista and Windows 7), Outlook 2007/2010 and Directory Opus (via my bundled plugin).
Adobe Reader comes with Adobe’s PDF preview handler but the installer had a mistake which meant the preview handler did not work on 64-bit systems.
It turned out the problem could be fixed via a simple registry change. The change is described below and a small program which performs the fix is also provided for your convenience.
Unlike the thumbnail fix, described below, the preview handler fix should no longer be needed by most people, since Adobe have finally fixed their installer, but it’s still provided in case it helps repair things. If you had Adobe Reader installed under Vista and later upgraded to Windows 7 then you will probably still need to run the preview handler fix once to clean up a registry value which Adobe set inconsistently between the two OS versions. If in doubt, run the fix and it will tell you if anything needs to be done. If everything is good already then the preview handler fix won’t change anything.