Trying to get the most out of 48V 500mA switch
Short answer: No, you can't use a resistor to reduce the voltage seen by the switch in your circuit.

It's the voltage difference across the component's terminals that matters, not the voltage at the component.

In your circuit, when the switch is closed the voltage across it is (close to) zero:



When the switch is opened, it will see the full voltage of the source across its terminals, regardless of the resistance of the rest of the circuit:



The purpose of a switch is to extinguish the arc that forms whenever a current-carrying circuit is interrupted. If the voltage and/or current exceeds the rating of the switch, the arc will not be interrupted quickly enough which will cause damage to the contacts of the switch, and eventually cause it to fail. In extreme cases (hundreds of volts and hundreds of amps) the arc will not be interrupted at all and the switch will fail catastrophically (think sparks, fire, molten metal etc).

If you want to operate your light bulb at a higher voltage or current than the switch is rated for you will need to use an interposing relay, like this: