Is there a way to update copies?

[DianaPuigferrat]

Is there a way in illustrator to have a copy of the object and if you make changes to the original it updates the consecuent copies of it automatically ?

[SJRiegel]

You can do this by using the Transform effect instead of making copies. Each instance made by that effect is changed by any changes made to the main instance. 

Another way is to may the object into a symbol. You could then edit the symbol to make changes to all instances.

[Ton Frederiks]

Starting with an object as a symbol would make that easy.

For copies of non-symbol objects you could try Global Edit