For shapes, chart elements, text boxes, and table cells, you can choose a line style and color for the object’s border, or you can specify no border. You can also put a border around imported images. You set border line style and color using the Graphic Inspector and the Colors window.
Select the object that you want to modify.
Click Inspector in the toolbar, and then click the Graphic inspector button.
Choose Line from the Stroke pop-up menu.
Choose a line style from the pop-up menu. For tables, only a solid line or None is available.
To change the line thickness, type a value in the Stroke field (or click the arrows).
To change the line color, click the color well and select a color.
To give the line endpoints, such as arrowheads or circles, choose left and right endpoints from the pop-up menus.