If you use WebDAV to manage Pages, Numbers or Keynote documents on iPhone or iPad
After you’ve updated to Pages, Numbers or Keynote 10.0 or later, you won’t be able to upload documents to a WebDAV server. To make sure you don’t lose any changes that haven’t been uploaded, save any pending uploads to your device, iCloud or another location.
If you have any pending uploads to your WebDAV server after updating Pages, Numbers or Keynote, you’ll see an alert asking if you want to recover documents with pending uploads. Tap Save a Copy to save one document or Save Copies for multiple documents, then choose a location on your device, in iCloud Drive or in another location. If you don’t want to save these changes, tap Delete (or Delete All for multiple documents).
Any documents you’ve uploaded to your WebDAV server before updating Pages, Numbers and Keynote on your device will still be available on your WebDAV server.