Hey I have a paid download app which I want to transform to a free download with in app purchases. The question I have is how do I make sure that those who already paid for the app doesnt have to pay again for the features?
From paid to free
When you change business models be sure that changes aligns with a new application version. This allows you to distinguish between who first downloaded your app while it was paid vs free.
In the App Receipt will see original_application_version which tells you the first version the customer purchased so you can determine if features are to be unlocked or IAP’s need to be purchased or validate existing purchases in the same receipt.
Here’s more info on where you can find the original_application_version https://developer.apple.com/documentation/appstorereceipts/responsebody/receipt