You can easily set a password to protect the user interface of novaPDF. This way, everytime the app will be opened, a password will be required to modify its settings.
Current password
If the interface is already protected with a password, you'll need to enter it here in order to pick a new password to protect it.
New/Confirm new password
Enter the new password and re-enter it in the Confirm field in order to set it as the new password that protects the user interface.