You could create a project for each app (so you won't have to change the project settings, e.g. name, icons, bundle identifier, ...) where you add the different PDF files and setup the storyboard screens.
Then you would create the classes in one project and drag & drop the files to the other project but uncheck the Copy items into destination group's folder option. That way you can change the code in any of the projects and it will be updated in all of them. You still have to build and submit each project on its own.