Is their any plugin for QGIS which would help me in exporting the map document as a GeoPDF ?
Let me quote Andreas on the mailing list (Status Feb 05, 2012):
Update Nov 2012:
But at least QGIS via OSGeo4W is still built with GDAL/OGR 1.9.
You can also check Latuviitta's guideline about "Making geospatial PDF maps from OSM with GDAL": http://latuviitta.org/documents/Geospatial_PDF_maps_from_OSM_with_GDAL.pdf (PDF).
Not Quantum GIS, but with GDAL.