I have found Google Keep an increasingly useful App, especially given the new integration into Google Doc’s.
MetaPDF allows you to create notes drawn from your annotations on any given document. It would be useful if these notes could be exported to Google Keep, or even better, if Keep could be integrated with MetaPDF so that annotations formed notes directly into Keep (Rolls Royce solution).
Such integration would obviously allow the user any easy route into getting notes from Paper Pile to Doc’s. Notes that can be ordered as required, coloured and tagged. Being able to reference the notes would be the icing on the cake.