Upload attachment via HTTP

Very often, a paper's author will put a copy of the paper on their website. And usually I want to keep my own copy. Currently, I need to download it to my local PC and then upload it back to my drupal as an attachment in the biblio entry. It would be nice if I can get biblio/drupal to download the attachment directly from the website.

(Probably this is not a biblio issue. Maybe what we need is a File Upload module with this capability? Does it exist?)