How to go from a Paid subscription App to a Free subscription App:
- Changing the price tier for all existing future Newsstand issue bundles from Tier 1 to Free (in iTunes Connect).
- Remove the 'In-App Purchase ID' of each issue (Published) and republish the issue before submitting the new build for to Apple.
- Removing the information for Apple Subscriptions in the App Studio build form and submitting the new build to Apple.