New notebooks that use the default style sheet shipped with Mathematica are set up to use the Working environment onscreen and the Printout environment when printing. Because of this, the print version of a notebook will look slightly different than the onscreen version. If you want the print and screen versions to be identical, the screen and printing environments must be the same.
You can set the style environment used for printing or for on-screen use. To set the screen environment, go to
Format Screen Environment
and choose from the available environments listed. To set the printing environment, go to
Format Printing Environment
. This allows you to display a notebook in one environment but automatically get printouts in another environment.