The Page Setup dialog allows you to control the size of printed output, plus other printing options.

Scale values less than 100% reduce the size of printed images and values greater than 100% increase the size. 100% corresponds to 72 pixels per inch, about the unzoomed screen size of the image.

The size of the printed image is determined by the Scale value and the width and height of the image in pixels. Spatial calibration is ignored.

Check Draw Border to have ImageJ print a one pixel wide black border around the image.

Check Center on Page and the image will be printed in the center of the page instead of in the upper left corner.

Check Print Title to have the title of the image printed at the top of the page.

Check Selection Only to print the selection instead of the entire image.

Check Rotate 90° and the image will be rotated 90° to the left before being printed (ImageJ 1.33m or later).