This is done with the use of a "Trim Cutter" or "Chopper" which is placed in the trim lines and actually cuts the material with a set of knife blade.
Once the material has been cut it can usually be conveyed very efficiently with the use of an LS fan wheel boasting a reduction in horsepower when compared to a traditional paper handling wheel.
Note: Using a "chopper" increases the static pressure which must be designed into the horsepower of the conveying fan. The amount of static pressure varies with different types of choppers and air volumes. ASDI includes this loss in the design of their systems.