I have done this:

To change the name of page_2, page_3 or page_4

open the appropriate file includes -> languages -> ENGLISH -> page_?.php

make the changes to fit your needs
define('NAVBAR_TITLE', 'Page ?');
define('HEADING_TITLE', 'Page ?');
then save the file to

includes -> languages -> ENGLISH -> CUSTOM -> page_?.php and upload to your server.

I didn't have a custom directory, so I created one, didn't work. It did change the header on the page, but it still says "Page 2" in the side box. Please help...thanks.

This is what I changed everything to:

// $Id: page_2.php 1969 2005-09-13 06:57:21Z drbyte $
//

define('NAVBAR_TITLE', 'Product Lines');
define('HEADING_TITLE', 'Product Lines');

define('TEXT_INFORMATION', 'Product Lines Offered');
?>

I am using the latest Zen Cart and 12leaves litegrey template.

Thanks.