Users have different experiences. There is no single solution that works for all of the iOS app update problems.
If you search using words like "iOS app update stuck", you will find a ton of hits on Google. The problems are not specific to Adobe Acrobat Reader. However, we hear about the problems from more users via app store reviews and our online bug reports whenever iOS has large updates that coincide with Acrobat Reader releases.
We have the FAQ document (which I mentioned in my previous forum reply).