Hello,
Please try following steps:
- Within Microsoft Outlook 2010, go to "File" menu and click "Options".
- Select the "Trust Center" link.
- Click on the "Trust Center Settings..." button.
- Select the "Attachment Handling" menu.
- Click on the "Attachment and Document Previewers..." button.
- Locate the "PDF PreviewHandler" option from the "File Previewing Options" list.
- To enable the PDF File Preview option, place a check in the "PDF PreviewHandler" checkbox.
8. Click "OK" to apply the changes.
Or try repairing Reader by Help -> Repair Reader Installation.
Regards,
Anoop