Hello Mels100,
Thanks for posting in the Apple Support Communities.
How exactly are you editing the files? What program are you using to perform the edit? We ask this because generally you'd view this file type in Preview which provides limited editing options.
Find files on your iPhone or iPad in the Files app - Apple Support
"How to edit files in the Files app
To edit a file, just tap to open it. Depending on the file type, you can:
- Use Markup to draw, add text, add a signature, and more
- Edit the file in Pages, Keynote, Numbers, and other apps
You can also delete files from the Files app. Changes to files stored in iCloud Drive or other cloud services automatically update on all of your devices. "
Also, what actions are you performing to save the changes you make to your document? Have you tried saving it under a new file name after an edit is completed?
Best regards.