In versions 7.5 and above there is an option in the attributes of the article for no index.

To view this option go to: Dashboard > Publishing > Folders

Select the article you wish to apply the no index tag

Click "Edit Attributes"

Expand Metadata > Meta Tags

In the Meta Robot Tags section tick the "no index" check box

Click "Publish"

If the website is on a lower version then 7.5 you could create a MasterPage for the article you wish google to not follow and add the META NO FOLLOW tag directly into the MasterPage.

<META NAME="ROBOTS" CONTENT="NOINDEX, NOFOLLOW">