Pullup use

I am using PMW on a FEZ Pico like below. I need to set the pullup on PB8 to pull high. How do I do that? Thanks

        var controllerPort = GHIElectronics.TinyCLR.Devices.Pwm.PwmController.FromName(SC13048.Timer.Pwm.Controller16.Id);
        var channelPort = controllerPort.OpenChannel(SC13048.Timer.Pwm.Controller16.PB8);

PWM is an output and therefore there is no such thing as pull up or down

Why would you need a pull up on a PWM output line?
The microcontroller will be pulling it either high or low, there will never be a floating state.