The unit has a display that shows output voltage. That display is ONLY accurate if you put either a 50 ohm or 1K ohm load on it, and select the appropriate command. If you do not have that correct load impedance...the actual voltage delivered to the load will have an error on it. That is not really a problem...you just have to set the unit to a different output voltage. The key here is to not have a voltage on the control pin higher than the switch can handle, or you might blow it up. Like if you told the unit to expect a 50 ohm load, but had a high impedance load instead.
If you plan on high speed switching, I would put a 50 ohm resistor to ground right at the switch, connect the switch to the pulser with a coax cable, and select 50 ohm load impedance. You will have accurate voltages, and less of a pulse reflection.