Rigid PVC and PVC foam sheet may be cut with a circular saw (using a very fine-toothed blade made for plastic panels, veneer or plywood). For best results, it is often better to cut just a few corrugated panels at a time to reduce vibration. Clamping the panels also helps. (But be careful clamping multiwall to avoid compression.)
If using a standard circular saw blade, better results may be seen by running the blade backwards (remove and turn it over to reverse direction). Depending on thickness, some panels may also be cut by hand by carefully using tin snips or a utility knife.