Do you just mean you want the 'print' button (that you hid in its event handler) to come back again? If so, you need to give it an id, and then do:
document.getElementById("print_button").style.visibility = '';
(Note: I usually use .style.display instead, but I think that makes little difference.)
Or if you want it to come back immediately after window.print() is called you can inline it in the event handler:
<input type="button" value="Print" önclick="this.style.visibility='hidden';window.print();this.style.visibility=''" />
However, this is all rather pointless since if you didn't provide the button at all, the user could just use the browser's Print button!
You can also use CSS to show/hide elements for printing, see for example this article