Not just FileReader - all Readers and Writers. It's crucial that you understand the difference between text files and binary files.
please,tell me how to use pdfbox within the android
I have no idea whether PDFBox works on Android, but I pointed you to a resource that explains how to get an InputStream from a file on an SD card, and it seems that PDDocument.load can use an InputStream as well as a Reader. What else are you looking for?