How is the article viewed? 

• If it's on the portal, you'd have to modify the widget responsible for displaying it
• If it's on the backend (which I doubt, but it's still an option), you'd have to modify the UI Page responsible for displaying it

I'm not doing anything fancy - they're just clicking "knowledge base" and then my article. So let's assume "portal". Is it just a matter of finding the right "portal" table to target then? Is there a service now default "portal kb" table I would use?

No, it's not about targeting the table at all. If it's on the portal, you'd ahve to update the widget responsible for displaying the article and include your code there.

So a client script won't work at all?

Try setting the client script to run "onLoad".