What should I do with a paper I've translated?
If the paper you are speaking about is a published research paper, you should contact the publisher (e.g., Springer), as they do deal with copyright issues. If the paper is a technical paper, written by a set of authors about a subject, and those papers are hosted on an university website or a research-based company, then you need to contact the authors. 

If the paper is not a research or technical paper, then well the question is not related to the Academia section.