If you use WebDAV to manage Pages, Numbers, or Keynote documents on iPhone or iPad
After you update 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 that asks 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 that you uploaded to your WebDAV server before updating Pages, Numbers, and Keynote on your device are still available on your WebDAV server.