I've never used a plasma cutter, but for most tools cfm is the limiting factor more than psi. Psi will determine how much air your tank will hold, and how high you can inflate a tire, but tools work on the volume of air coming out of the nozzle.
The plasma cutter works, by blowing air across an electrical arc. Some of the air turns into plasma, creating the focused heat, and the rest blows the molten metal out of the cut. You'll need a lot of air to do this for very long. If you try to use the pancake compressor, it won't be able to keep up with the needed cfm. It may start putting out enough, as the flow out is controlled at the nozzle, but the compressor will be putting less air in than is coming out. So at best you'll be able to cut for short bursts in between waiting for the compressor to fill back up. If this were a standard pneumatic tool, you could do a little bit, wait, do a bit more, wait, and so on. Whether even that is doable with a plasma cutter, I don't know, it depends how long they take to start the cut.
In short, you'll very likely need a higher cfm compressor if you're going to do much cutting. Whether you can do a little cutting without one, I don't know.