How to go from a Paid subscription App to a Free subscription App:

  1. Changing the price tier for all existing future Newsstand issue bundles from Tier 1 to Free (in iTunes Connect).

  2. Remove the 'In-App Purchase ID' of each issue (Published) and republish the issue before submitting the new build for to Apple.

  3. Removing the information for Apple Subscriptions in the App Studio build form and submitting the new build to Apple.