The invention provides a printing system with a transport mechanism for transporting sheets. The transport mechanism comprises: a conveyor body for supporting and conveying a plurality of sheets a transport path; suction means, and especially fan means, for generating an under-pressure at or adjacent to the conveyor body to hold the sheets fixed in position on the conveyor body as it conveys the plurality of sheets along the transport path; and a controller for controlling or regulating operation of the suction means to adjust the under-pressure generated. The controller is configured to control operation of the suction means based on delivery of the plurality of sheets to the conveyor body and/or a change in the delivery of the sheets to the conveyor body. Further, the invention provides a corresponding method of transporting sheets of a print medium in a printing system.