I have an application in App store that uses app id without "in app purchase" option enabled. I'm going to add this feature in further versions. What options do I have?
Do I need to create a new app id with "in app purchase" option? (is it allowed for existing applications ?)
If your current App ID has a wildcard character, such as "com.myApp.*", or "BDQ78GF.*", then you'll need to create a new one in order to be able to use In App purchases for it. If it doesn't, then you should be able to enable them from within the iPhone Developer Portal.
Craig was party right...however, if your app does not have wildcard you will have to create a new one...but NO you cannot just enable the option in the iPhone Developer Portal and not worry about resigning your app. You must rebuild the app with the new Cert. In-app purchase and push both require "push" enabled certs...which you have to rebuild the app with.