Adobe Illustrator normally uses the default page size defined by the PPD file for the selected printer. However, you can change the media size to any of the sizes listed in the PPD file as well as specify portrait (vertical) or landscape (horizontal) orientation. The largest page size you can specify depends on the maximum imageable area of your imagesetter.
Note: Changing page size and orientation in the Print dialog box is for printing purposes only. To change the page size or orientation of your artboard, use the Artboard Options dialog box or the Artboard options in the Control panel. (See Edit artboards.)
Note the following when specifying the page size and orientation:
If you select a different media size (for example, if you change from US Letter to US Legal), the artwork is repositioned in the preview window. This is because the preview window displays the entire imageable area of the selected media; when the media size is changed, the preview window automatically rescales to include the imageable area.
Note: The imageable area may vary by PPD file, even for the same media size (for example, US Letter), because different printers and imagesetters define the sizes of their imageable areas differently.
The default placement of the page on the film or paper depends on the imagesetter used to print the page.
Make sure that your media size is large enough to contain your artwork as well as trim marks, registration marks, and other necessary printing information. To conserve imagesetter film or paper, however, select the smallest page size that accommodates your artwork and necessary printing information.
If your imagesetter can accommodate the longest side of your imageable area, you can conserve a considerable amount of film or paper by using Transverse or changing the orientation of the printed artwork. Consult the documentation on your specific printer for more information.