Change a free app to a paid one

I have released a free app on the App Store, and some users have already downloaded it. Recently, I want to change this app to a paid app. I would like to know if users who have already downloaded the app will need to pay for it. I understand that if users still have the app on their device, they can update it for free; but if users have uninstalled the app, will they be required to pay when they download it again?

Change a free app to a paid one
 
 
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