Did you re-start your iOS system?
Yes, there was an update available so I updated it and completely re-booted it.
[topic moved to Reader/Acrobat DC for Mobile forum]
Try removing the app and reinstalling it.
Be aware that on an iOS device deleting an app will remove all your PDF files. Make sure they're backed up.
Sorry for the problem that you have been experiencing. Unfortunately, the problem can only be fixed by uninstalling and reinstalling Acrobat Reader for iOS.
Please take a look at the following FAQ document to properly backup your PDF documents first.
After you ensure that you have the backup copies of your PDF documents
- Uninstall the app.
- Download and install the app from the App Store.
- Restore your PDF documents using iTunes.
Please let us know if you have additional questions.