Bipolar signal amplifying to high voltage
A transformer with 15:500 = 1:33 ratio can do this.

Be aware though that while this amplifies the voltage, it also reduces the current capability.  Voltage times current is power, and you can't get power more power out of a passive device than you put in.

For example, let's say the &plusmn;15 V signal is capable of 1 A.  After a 1:33 transformer, it will be &plusmn;495 V with a maximum theoretical current capability of 30 mA.  In reality, there will be some loss in the transformer, so the actual output current capability will be less than 1/33 of the input current capability.

Since actively driving a signal at &plusmn;500 V is a lot more difficult than doing it at &plusmn;15 V, you should amplify the signal before the transformer.  The only component that touches the high voltage output is the transformer.  No other circuitry is required at the high voltage, and no high voltage power supplies are needed.