All local applications
You can use GoEdit with all applications you have installed on your local PC or Mac.
Default
If you want to use GoEdit to edit a specific attachment, be sure that the application you want to use is the application that would be opened when you double-click on the file locally (when you download the file manually).
GoEdit always uses the default application to open files
Can i uses cloud applications
You can not use applications like Google Docs or other browser based (cloud bases) applications, since you do not have them installed on your PC or MAC locally