You can add free-hand drawing to the drawing layer of the sheet using annotation mode. Annotation mode allows the user to draw in free-hand mode on the shapes layer and to save the annotation on the sheet as a shape.

Use StartAnnotationMode and StopAnnotationMode to turn on and off the ability of the user to draw on the drawing layer. There are corresponding events, AnnotationModeStarting and AnnotationModeEnding. You can also customize what occurs using the OnAnnotationModeStarting and OnAnnotationModeEnding methods.

By default a thin black line is drawn. You can change this and you can pop up a dialog for the user to select the drawing pen or stencil or bitmap pattern.

Use the CloseFigure method if you want to close the drawing between the start and end points with a straight line.

You can use the CancelAnnotationMode to cancel annotation mode and return to normal cell editing mode.

For more information on built-in and custom shapes that can also be placed on the drawing layer, refer to Working with Shapes in Code.