Assuming you have the free version - 'Adobe Reader', try this.
Open the program and click on Help from the menu options in the top left hand corner, from the dropdown menu which appears select 'Repair Adobe Reader Installation'.
If that doesn't fix the problem and you do need to uninstall and re-install, go to Control Panel, click on Adobe Reader in the list and then click on uninstall.
Then do a web search for Adobe Reader and follow the download instructions.
You only need one download to open PDF files, whichever browser you're using.
If you have the paid for full version - 'Adobe Acrobat', the procedure is going to be similar, but will probably ask you for a licence/registration code number. I don't know though as I only have the free one.