The current E2CP configuration only supports one (1) URL for adding Public KB Articles to Case Emails. An Idea has been created that supports extending the configuration to allow for multiple Public KB article URLs.  If you are interested in this idea, please click here and vote up this idea.

If you need assistance with including Knowledge Article Links to your Public Knowledge Base (PKB) in Emails, you will find the instruction you need here:
http://kb.internetcreations.com/?kb=000001212