Mupdf
MuPDF is free software: you can redistribute it and/or modify it under the terms of the Affero GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
Here's a link i found on SO. List of few pdf libraries helful
https://stackoverflow.com/questions/4665957/pdf-parsing-library-for-android/4766335#4766335