Unless this is a piece of shameless advertising, your PDF that you want to change...
This
<td width="369" align="right" valign="top"><a href="Hot-Woks-Cool-Sushi-catering-menu-2013.pdf"><img src="images/featured/hot-woks-catering.jpg" alt="a cultural evolution of taste" width="369" height="413" /></a></td>
the element you need to alter is simple.
<a href="Hot-Woks-Cool-Sushi-catering-menu-2013.pdf">
which should according to the W3C have at the minimum the title element as well.
<a href="Hot-Woks-Cool-Sushi-catering-menu-2013.pdf" title="Our Hot Woks Cool Sushi Menu">
and that helps your users with accessibility devices.
To get the item to download...
<a href="Hot-Woks-Cool-Sushi-catering-menu-2013.pdf" title="Our Hot Woks Cool Sushi Menu" target="self">
If you have updated your menu called "Hot-Woks-Cool-Sushi-catering-menu-2013.pdf" then your new menu must be in the same folder as the page that loads, so if this in the site root, the new PDF has to be in the site root. you only need to change the href information to point to the new file.