Being unable to uncheck this box is not something I've come across myself but something else you could try is to edit the Kobo config file directly rather than via the GUI:
- Connect H2O to PC and navigate to the file .kobo/Kobo/Kobo eReader.conf
- This is just a simple text file, so open it in your preferred text editor.
NB it needs to be a text editor which understands Unix line endings. On Windows, the built-in Notepad is NOT suitable but the free Notepad++ is suitable.
- Find the existing section with heading [Reading] and look for readingAdobeShowPageNumbers it should read
Code:
readingAdobeShowPageNumbers=false
If you can't find it you'll need to add the line yourself.
- Save and disconnect safely. I'm not sure whether a full power off/on is also necessary.