Moving a single license app to Pro

Hmm, good question. Updating the app is easy: replace the app in the store with a new version that was based on Pro, with multi-issue support. People who have already paid for and downloaded it will get an update that changes it to the multi-issue version.

The bigger challenge is entitling the previous purchasers to the issue that was previously bundled into the single edition app. I can't think of any way to do that for your previous paid users since you have no idea who they are. Honestly I would say don't worry about it and just make the issue that was previously included in the Single Edition app as free to all of your users, even ones that didn't pay for the older version of the app. In the grand scheme of things it likely won't cost you very much, provides your potential subscribers/purchasers with sample content, and is zero hassle for you

Neil