In the PDF Editor, you can use the Comment tab to draw freehand, add handwritten notes, highlight text and erase on your PDF.

To draw, write, or highlight text, click the Pen or the Highlighter icon and move your cursor. Click the drop-down arrow to customize the stroke color and thickness. Click More colors if the color you need is not in the palette.

When you are done with drawing, writing or highlighting, click the Pen or Highlighter icon again, or press the Esc button.
Click the Eraser tool and move your cursor back and forth to delete a stroke. The Eraser deletes only the whole stroke.
Use the Select button to select the inscription, the drawing or the highlighting. Once selected, you can resize or delete the selected element.