I already have a free version of my app in App Store. Now I want to add a completely new paid version of the same app (with extra features).
Is it required to implement In-App-Purchase or can I simply add the paid version as a new app?
You can create a paid version of your app with no problem. It will get approved. So it's really up to you. But using in-app purchase makes it more convenient to the user. They will be able to switch to full version of the app without losing any data (like achievements for a game, or documents created with the free app).
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