Sorry about my confusing language, what I meant was the input signal is 1v p-p at the input test point of the output amplifier.
If you lower the AC with the vernier instead of the range switch, can you get a large DC offset relative to the AC level - in other words on a particular output amplitude range, is the DC offset setting separate from the amplifier amplitude control knob? If it is, I think you will have no trouble generating, say, a 5vpvp squarewave going from 0v to5v.
If you want 1uV sinewave output on a 10Vdc signal, you just use an external 10V DC source and 50 ohm resistor in series and connect the generator via a capacitor between ground and the 50 ohm resistor.