Here’s how to fix this error when you try to invoke an application (Acrobat Reader, Excel, etc) by 2x clicking on the attachment. In this case, our problem was with PDF attachments.
Go to Windows Explorer. Click on Tools>>>Folder Options>>>File Types
Find “.PDF” in the extension list on the left. The right side “File Type” list will incorrectly display “PDF File”. This is how you know the link is incorrect.
Click Change, and associate the file with the correct program, in this case AcroRd32.exe.
File Type should now be “Adobe Acrobat Document”
Click Advanced>>>Edit
Make sure “use DDE” is unchecked (no check mark in box). You are finished.
Try to open a PDF attachment in Lotus Notes, it should now work with no problem.