I found an excellent module for this and it works really our of the box using admin.

https://drupal.org/project/node_buttons_edit

I found the excellent Node buttons edit module for this and it works really our of the box using admin. Here is an excerpt about it from the module's project page:

This is a simple little module that allows one to change the text on the 'Save', 'Preview' and 'Delete' buttons on a node form.