There are many ways to duplicate objects in Illustrator. The simplest is to select an object (or objects), hold down the Option (Mac) or Alt (Windows) key, and click and drag. When you release your mouse button, you place a copy of the selected paths on your artboard (Figure 36a).
Figure 36a Copying with the Alt or Option key.
You can also copy and paste selected objects by choosing Edit > Copy from the menu. There are three paste options available from the menu. In addition to the regular Edit > Paste, you can also paste in front or in back.
Illustrator allows you to manage stacking order as you paste. Edit > Paste in Front stacks pasted objects on top of other objects, and Edit > Paste in Back stacks pasted objects below other objects (Figure 36b).
Figure 36b Pasting an object in front of other objects.
You can use the Copy and Paste commands to transfer objects in and out of Illustrator. Copying and pasting through the clipboard is more reliable if you are transferring files to or from other CS3 applications, like Flash or Photoshop.