Adding a DC level of 1 volt to a waveform shifts the entire signal upward by 1 volt in the time domain, resulting in a new baseline. In the frequency domain, the addition of the DC offset introduces a spike at 0 Hz, representing the constant component. The RMS value of the waveform will also increase, reflecting the added DC level, which can be calculated using the formula that combines the original RMS value with the DC offset. For example, if the original signal had an RMS of 2 volts, the new RMS would be approximately 2.24 volts after adding the 1 volt DC offset. Overall, the waveform's characteristics in both domains are altered by the introduction of the DC level.