How to show app ad's only to new users? I have an app in the appstore that used to be paid and with no ads. 

I want to upload an update, make the app 'free', add ad's, that could be removed by purchasing "No ads 'in-app purchase'". 

Problem: 

I don't want users that have paid for the app before to update the app and see ads. 

I want to grant "No ads 'in-app purchase'" for users who is updating the app. 

Basically, if a person is updating, then no ads is 'purchased' by default. 
If a person in downloading the app for the first time, he gets ads. 

Is this possible? Any workarounds? 

Thank you
You could update the paid app to set a preference that the user has the paid version. Then update the app with the free version.