To print a plot, select the plot item in the Plot Tree, and select Print current plot... from the File menu. The layout of the plot can be adjusted (Page Setup), and previewed by selecting Print preview (current plot)... from the File menu.
To setup the page layout for printing, select Page Setup... from the File menu.
This dialog allows adjustments to the paper orientation, margins, centering, and overall plot scaling. By default, all printed plots are scaled to fit the page (withing the margins and maintaining the original aspect ratio). A scale value of 100% maintains this size, while higher/lower values result in a zoomed plot image.