I'm happy to be corrected by anyone who knows better but, to the best of my knowledge, this is not a feature in Aperture. You would have to edit in Photoshop or another external editor that has this facility.
However, if you print direct from Aperture you do have the option of setting the print resolution. Dependent on the file dimensions and the paper size, you may or may not get a little yellow warning triangle in the corner. What Aperture is doing under the hood, I've no idea - perhaps someone with more technical savvy could comment?
I've never tried upping the print resolution like this direct from Aperture but will give it a try over the next day or so and compare with upping resolution in P'shop.