Disable Automatic Update "Company Wide"
                        
                            - Open the Application or Outlook Add-In and choose   
- Go to the Company Settings Tab.
- Check the Options "Only Prompt for Required Upgrade"
- Click ok
Now, everyone in the company will not be prompted to upgrade.
                        Disable Automatic Update for a "User"
                        
                            - Go to the Application or Outlook Add-In Interface and choose Settings
- Go the on the General Tab at the bottom is 2 options and check both.
                            
                                - Do Not Remind Me Until Next Version
- Do not Prompt for Upgrades on Startup
 
- Click Ok
Now, this user will not be prompted to upgrade.