You can add shape annotations in the form of straight or free-form lines, squares or rectangles, and circles or ovals.
- Click the desired annotation tool button—Line
to draw a straight line, Pen 
to draw a free-form line, Multi Shape 
to draw a few free-form shapes at the same instance, Rectangle 
to draw a square or rectangle, or Oval 
to draw a circle or oval—and draw the shape on the image.
Notes:
- Press the Shift key to keep the straight line perfectly horizontal or vertical.
- Press the Shift key to create squares or circles with the Rectangle and Oval tools.
- Use the Multi Shape tool to mark a few items at the same time, when you complete drawing the shapes, click Done and type the required comments.