Write on existing pdf

I am sure there is a good answer for this question that I do not know of it. I am wondering if there is a way that I could draw 2D elements on a pdf file. I have a pdf file with few hand sketches and I want to load this in Gh and add few shapes to it and then bake the shapes on pdf and save it. I am looking to use capability of Rhino to do markup on pdf files. This really makes my life easier as I do these things by hand or Bluebeam which takes ages to complete. Appreciated. Mano