When you submit an iOS app to App Store review, the review process adds to its filesize. Exactly how much is the sub process adding? We have been attempting to submit our app and want to have tit available for OTA download. This means we have to keep it under 100 MB. Unfortunately we have been rejected several times because the amount that is added by Apple during the submission process appears to have greatly increased during the last month or so.
Having been through the submission info on the iOS Developer Library multiple times, the only referrence I can find to this is on https://developer.apple.com/library/ios/documentation/LanguagesUtilities/Conceptual/iTunesConnect_Guide/Chapters/SubmittingTheApp.html, and the only infomation given there is that the app has to be under 100 MB.
Since this extra filesize is added by Apple, after the app has been created and submitted, developers REALLY need to know how much you add!
The review process adds hardly anything anything to the size, but as this tech note explains, final encryption can cause the file to be larger. There is no set number for this, the size increase is dependent on the contents of the archive.
It also gives hints on how to reduce your file size.
https://developer.apple.com/library/ios/qa/qa1795/_index.html
With the advent of iOS 9, app thinning will allow you to have assets stripped out that a specific device user will never use and so make the overall download size smaller.