Web Personalization Segments Filter Question

Hello - we are trying to launch a web personalization dialog campaign. The campaign will promote a white paper to specific segments that visit our site. Here's the workflow for downloading the content - dialog displays button with UTM hyperlink, which takes the person to a landing page that contains the form for the content download. Web segments are using named account lists and personas for main filters. We are fairly confident in how we have everything set-up but are still trying to figure out the best way to exclude someone in the web segments who has previously downloaded the content we are promoting. Any thoughts on the best way to go about this?  Thanks!