The latest version of Texture Maker is:

Texture Maker can automatically check to see if it is the most recent version and take you to the download site accordingly. Simply start Texture Maker and click on the Help menu and select Check for Update...

You must have an active Internet connection for this to work. If you are using any Firewall software you must permit the Texture Maker application to pass through this otherwise the check will fail. Eventually you'll see the following screen (or one similar) - click the link given to access the download site.

As an alternative to using the built-in version checking you can simply download the Trial Version of Texture Maker (available from this site) and install it. It will recognise that you have a full version of Texture Maker and update the program automatically. It will not revert back to "Trial" mode so long as your copy of Texture Maker is fully registered.