How can I purchase Craft Client or Craft Pro? Docs say 'Right within Craft. If you’re running Craft Personal or Craft Client, there’s a link at the bottom of every page in the CP, which brings up a modal window that handles the whole process.'

I just installed Craft Personal 2.3.2629 and there's no link I can see.
Go to the Settings page (/admin/settings - reached by clicking on the gear icon at the top right of the control panel) and you should see the following link at the bottom of the page:



Click on the Show me link and the modal window pops up.