I think that the engine is great but the integration of the PdfView is not really easy. I would suggest to add the ability to easily customizing at List the reader. Also it would be grateful to have a ready to use pdfView witch can be integrated with an existing application in 1 day. Also I think that the sdk must include an wrapper to handle the matrix transformation complexity.
The sdk will be used in most case in Android Tablet, within a phone we can start an intent to read a pdf file, but in tablet the needs to read files within a Fragment is more signifiant. so i suggest that the demo version will target the Android tablet. I invite you to see our Ipad application that we are facing problems to port to Android Tablet.