Print to Scale mode is a print option that sets up a one-page scaled version of your model.
With Print to Scale, your print preview is rendered using SketchUp's parallel projection camera. You can still pan, orbit, and zoom your model in the preview pane. When you zoom you change the implied scale of your drawing. Changing the paper size also changes the implied scale.
To choose a specific drawing scale, type the scale you prefer to resize your print.