Compressed PDF

Using FOP 0.17 I obtained a PDF output containing normal (printable)
characters.
Now, with the same application but with 0.18 version, the generated PDF 
document contains special
characters (meaning that the produced format is a compressed PDF; the 
file size is smaller also).

- I have to use a StringBuffer to return the document.
- I specify a ByteArrayOutputStream to the setOutputStream() method.
- Once filled the output stream by render(), I return the StringBuffer 
as follow:
  return new StringBuffer(outstreamobj.toString());
But the problem is that:
- The StringBuffer constructor maps special characters (hex > 80) in 3F.
- Consequently, the StringBuffer contains a compressed (but incorrect!) 
PDF.

Is it possible to call the Driver's render() method asking for a non-
compressed PDF output ?

Thanks,
Gian Piero Canciani