How to select rated voltage of a RF capacitor
Rough calculation: -

A 33 pF capacitor at 850 MHz has an impedance of about 6 ohms. If it is passing a power of 33 dBm (about 2 watts) to a 50 ohm load, the voltage seen across the 50 ohm is \$\sqrt{2\times 50}\$ = 10 volts RMS.

The 50 ohm current will be 200 mA RMS and this will drop a peak voltage of about 1.7 volts across the series 33 pF capacitor.

So if the DC voltage plus the peak voltage is well below the capacitors rated voltage then you should be OK.