Editing Documents stored in OneDrive in Offline mode on an iPad
If you use the OneDrive app and you download a document to your iPad, you will not be able to edit the document unless you are online. This does not make sense.
I found a solution to this problem by using the Files App that comes with iOS 12.2. Using Files, you will find OneDrive on the left had side. Click on that and find the downloaded document. Click on the document and you will see that it opens normally for editing using the default app. Example a word document will be opened by Word.
Hope this solves the problem. I know it solved it for me.
iPad Pro, iOS 12