[Zope-dev] access of non html documents

i have the following situation. i want the users to be able to download non html documents if that document is refered to from an html document. however, i dont want the users to be able to type the url and document name on the url box of their browers and be able to download it. for example: the documents exist in http://www.wwwdotcom.com/nonhtmldocs/doc1.pdf however, i dont want the users to type that url on their browser and access doc1.pdf i only want them to access it if that particular document is linked from an html document. i have seen some websites that do that w/ images. how can i do that on zope? is it possible? i would appreciate any comments/suggesstions. -roberto