Try this out:
1. Right click on any PDF document -> Get Info
2. Click on Open with entry on the get info dialog
3. In the Application dropdown locate to your installed copy of Acrobat and select Acrobat application
4. Once you have selected Acrobat click the "Change All button below the drop down"
5. Click Continue on the user confirmation dialog
6. Quit the Get Info window
Wide information about ways to recover pdf file..