Is there a way to dimension a spiral in a drawing? I need to dimension the pitch.

If SW won't let you dimension to the model directly you should be able to place a sketched line (or lines) in the drawing view, with relations to the model, and then dimension this line.  After placing your dimension you can move the line to a Layer that's turned off if you don't want it to show.

I would mark the pitch dimension on the model "for drawing" and autodimention your drawing.

The pitch dim. will be shown automatically.

You can also open a 3d sketch and add points on the curve and on a plane that splits the helix. These would be available to you to dimension if you show them, or you could dimension them as driven and mark the dimension for import to the drawing.