Whenever you edit app settings such as app icon or launch images.
Whenever you want to take advantage of a new viewer features in a more recent release.
Whenever you upload new custom fonts.
When you make changes in the DPS Portal such as changing project settings, adding products or subscriptions, or adding content, you do not need to update your app. The one exception to this is uploading fonts, as I mentioned. (That team is hoping to upload custom fonts on the fly so that you don't need to rebuild your app.)