I use a jigsaw to cut it but it has to be done quickly and carefully, if it cuts too slow and lingers too long in any spot the plastic melts from the heat of the blade. Needs to be well supported to as it can crack easily along the cutting line, it's a good idea to stick a piece of masking tape on, mark the line and cut through then, it gives the jigsaw a bit of grip rather than wiggling all over the place.
There may be better ways to do it but this is the way I do it, easy enough to cut straight lines, lot more difficult to cut circles or curves I find.