A paper-pusher is someone whose job is mostly moving documents around an office — filling forms, stamping papers, sending files from one desk to another — work that does not feel important or exciting. It is not a kind job title. People say it when they want to sound a little scornful, as if the person only pushes paper and does not really decide anything. You hear it in informal, mostly American-leaning English; you would not print it on a name card. A manager who runs a company is not a paper-pusher; a clerk who spends the day on forms might be called one, fairly or not. Though actually a lot of office work really is paper, or the computer version of paper, so the sting is about status more than about whether paper is involved.