To obtain a duplicate of an object, you can copy it to the clipboard in the usual way and then paste it back from there.
Alternatively, you can also use the Duplicate button 
on the object-specific ribbon tab. This command immediately creates a copy of the selected object.
Note: An object-specific ribbon tab appears on the far right as an additional tab when you select an object.
Tip: Duplicating an object is even faster with the mouse: If you drag an object while holding down the Ctrl key, you immediately obtain a duplicate of that object.