It should be possible, but I doubt you could do this on a Marketo-hosted landing page, due to the need of server-side coding.
You should start by looking at the Marketo cookie and pulling down a unique identifier for the visitor on the landing page. I haven't looked at this myself, but the cookie probably has their email or Marketo ID that you can pull out. Use that to query them via the Marketo API and pull whatever data you need to then use against your content DB.
Here's the Marketo API page: http://developers.marketo.com/documentation/soap/