public byte[] readPdfBytesFromUri(Uri uri) throws IOException {
    InputStream inputStream = getContentResolver().openInputStream(uri);
    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
    byte[] buffer = new byte[1024];
    int length;
    while ((length = inputStream.read(buffer)) != -1) {
        byteArrayOutputStream.write(buffer, 0, length);
    }
    byte[] pdfBytes = byteArrayOutputStream.toByteArray();
    inputStream.close();
    byteArrayOutputStream.close();
    return pdfBytes;
}