Page Number in a PDF using DataExporter

[nuxero]

Hello, I want to put page numbers like "page X of Y" in a pdf generated using DataExporter.

I've searched before and I know that I can achieve it using PdfPageEventHelper or by a Two Passes approach, but I don't know how to implement it in neither preProcessor or postProcessor method, since I don't know how to get the OutputStream corresponding to the document. Here are the examples:

http://itextpdf.com/examples/iia.php?id=104
http://itextpdf.com/examples/iia.php?id=118

Is there any way to make it using DataExporter or should I drop DataExporter and use iText directly?