I watched this film a few years ago, I'd say it was released after 2010. I thought the main actor was either Elijah Wood, Jake Gyllenhaal, or Tobey Maguire, but a search on IMDB hasn't returned any results.
The film was about a boring guy who had no life. He used to go to work ad punch cards, file papers, etc... He was always on target but never did anything out of the ordinary. There was a girl he liked (if I recall correctly). No one really liked him.
Then one day a new guy turned up at work. Everyone like the new guy. He was funny. Etc...
But this new guy looked exactly like the boring guy (was played by the same actor).
And this new guy (if I recall correctly) would encourage the boring guy to break the rules, etc...
The film had a very dark theme to it. A very muted colour palette. Lots of browns and greys.
At the same time as being dark it also had an almost comedic sense. (Sort of). I remember he used to sit at a desk in a cubicle office but not like a usual one. It was reminiscent of an old fashioned train carriage (Sort of). He had a desk with a typewriter IIRC.
He would sneak looks between the cubicles at the new guy. He would try to ask people if they though the new guy was familiar or reminded them of anyone. Etc...
I'm sure the name of the movie was something along the lines of "Doppelgänger" or "Twins" or something that gave the impression of a copy.