If you’re trying add lines to your latex document, you’ll need the lineno package. For the ubuntu 12.04 users out there, you won’t find it with the texlive-latex-base package. In fact, it wasn’t even in the texlive-latex-extra (which was my first guess). Oddly, it was all along packaged with the texlive-humanities.
Oh, please don’t think I find it by my own means… it’s all about google!