Unable to view PDF from device storage

If i put file in raw folder application opens PDF file. but when i tried to open same file from sdcard it throws unknown exception.

File mfile = new File("/sdcard/chapter2.pdf");
mDoc = new PDFDoc(mfile.getAbsolutePath());

Please guide me with this.

Have you tried loading the file from /mnt/sdcard, and without using File? For example:

mDoc = new PDFDoc("/mnt/sdcard/chapter2.pdf");