kaarthik,
That's not possible actually. As I said PlanetPress can only send jobs to printers it's licensed for. If you want to print at your client's location using PostScript, then you would need to purchase a licence for their printed, send them the PlanetPress Design as a postscript file to install on the printer, and then send them the data file with an appropriate trigger.
This involves costs (the licence) and technical implementation (installing the document).
Alternatively, they would have to purchase their own PlanetPress Suite licence, or you would have to purchase it for them.