We are a sheet music publishing company. We will provide our customers with digital sheet music, however without the possibility to print or to share the music with others. So we will give them an app that functions as a library, in which we can put the sheet music (encrypted pdf format). The customer should be able to open the files, to view them both in portrait and landscape mode, to add remarks en to store the pdf's again, encrypted en including the remarks. The app should run onder Android and iOS.
There is more to tell, but that is the basic.