Can I use a jumper from existing light switch to get power to 5 new lights?
Most likely you can pull power from an existing work box that has a switch, as long as you don't overload the circuit.  This is a pretty common wiring task, but if you provide details or a photo of the wiring in the source box we can provide a wiring diagram.

If you are adding a switch where you have an existing single-pole switch that has both a hot and neutral conductor, then yes, you can "jump" from the hot wire that serves that switch to a second single-pole switch.  But you still need to make sure your additional lights won't overload the circuit: don't depend on the circuit breaker to determine what the peak load on the circuit serving that switch is!