Please follow the below mentioned steps to uninstall the iOffline reader: 

• Install the application "iOffline Cleaner"   
• Run the iOffline cleaner application 
• From the path Go -> Mac -> system name -> Library -> Preferences -> ioffline folder (with unique numbers): move to trash/delete[Hold down the Alt (Option) key when using the Go menu. The user library folder is listed below the current users home directory]
• MAC -> Application folder -> iOffline.app (delete the .app file) 
• Go to Trash and select “Empty Trash”.

Note:AIR application should be version 3.0 and above.