No reason you couldn't use a little Forms JS to pop up a Marketo form that gates content specific to each page. There would have to be a pointer to the content somewhere on the page -- for example, a <link rel="enclosure" href="https://download.example.com/a/specific.pdf"> in the <head> would be semantically appropriate. You could of course include any other descriptive info as well, and then use the Marketo Forms JS API to dynamically switch the thumbnail image on the form and the form's follow-up (Thank You) asset/page. You could store the whole page-to-asset config in one big JSON file if you wanted, and serve that file from Marketo (a Design Studio asset) -- that too would work in conjunction with the JS API. But there too, Marketo itself wouldn't know what you were using it for, all of the business logic & config would be on the client side in JS. Marketo does not offer a central place to link non-Marketo pages to specific assets/actions/popups unless you add on the Web Personalization module, which is a whole other ball of wax.
... View more