You can change the name of any document you upload by giving the document an "alias". Select the document you want to give an alias, then click the "Edit Document" icon Edit Icon in the document grid header. 

This will bring up a window for you to add a new alias or edit an existing alias.

When you save your changes, the document grid will now show the aliased name instead.

NOTE: The alias's you use are only visible to you, so feel free to use the alias "Smoking Gun" on your best document exhibit. Only you will see it.  You can view the document's original filename in the document viewer, the "Edit Document" prompt, and in the header of the deposition view.

Next: Add labels to your documents.