In responds to enabling full text search within pdf-attachments, several readers asked how they could also preview these pdf-files directly in Outlook.
This should work directly on a 32-bit version of Windows with the latest version of Adobe Reader or Adobe Acrobat installed. Sadly, the installer from Adobe does not write the correct registry setting to also enable the previewer on a 64-bit version of Windows.
Update: This issues has been solved in Adobe Reader/Acrobat X. You can still use the solution below if you are using Adobe Reader/Acrobat 9.
Note: This will also enable the PDF Preview feature in Windows Vista and Windows 7 itself.