This is a difficult question. I recommend you save your PDF to an image file rather than try to draw on it. You can do this by going to the File menu and selecting Export > Save as Image > Choose where you want to save your file, for example C:/My Documents; next enter a filename of .png (this will change depending on what operating system your using) – there should be a “.png” option at the bottom of the dialogue box; then click OK… You can now open up Paint or Photoshop and drag in that new .png file — it may need some refining before hand.”