Is it not called duplicated content using links of files (documents and images) from other sites in own site? For example, let say, I have a game blog, can I use game links hosted on other sites in my own site?
(documents and images) from other site is a part of content copying, if you want to position others site content in your site you have to take permissions form site owner of other site. If you not you are under content copying law. Regards,