Dear user, the way iOS manage files' and folders' permissions is a choice of Apple.
The only way to make a document be writable is to load it in a folder r/w accessible.
While distributing a file as preloaded resource in you ipa you should load it as asset resource.
Assets are in a read only folder.
That's normal way when interacting with iOS devices and mostly the same on Android.
Please, follow what my colleague was suggesting: run the application, open iTunes and load a new pdf file in the application space from iTunes interface.
The new pdf file will be loaded in a r/w folder and all the features from the demo will be available on your file.
