http://ez.no/community/forum/developer/fetch_main_node_id_in_relation it introduce the use of objects relations and helps us to fetch all your related object.
extend the article class with an "object relations" attribute and amend your template to loop round these and output them. This way you can relate other types in addition to files.
An easier approach would be to upload files into the media gallery and link to them through the online editor. I recommend the first as it takes care of the linking at the template level
An approach we use here is to present an upload form which stores files as child objects. That makes ti also easier to apply /implement roles and policies. The article needs to be published before though.