To expand the page edges so your graph fits on the page, click File | Page Setup. In the Page Setup dialog, click in the Size field to choose a new paper size.
If the desired page size is not listed, click Printer to select a new printer and driver. The page sizes listed in the Page Setup dialog are determined by the page sizes supported by the default printer. In general, selecting a PDF print driver as the default printer will provide the most page size options.
If you would like Grapher to support user defined custom pages sizes, please let us know.
Updated December 12, 2017