Depends on the internal resistance of the power supply.
At 100V peaks you'd get 10 mA of current. A power supply should be able to easily take care of that extra current.
In fact you could read a 100V signal with just a resistor on the Arduino pin, that's what the data sheet suggests. A 220k or greater resistor is all you need. Current <0.5 mA and the clamping diodes take care of the rest.