How to export a Prism graph or layout as pdf to fill an entire page?

When Prism exports to the pdf format, it trims away (crops)  the white space, leaving only a tny margin. This is what you want if your goal is to send the image to a publisher or embed it in a lab notebook. But what if you want a full page? Here are some alternatives:

• Copy the page or layout, and paste into Word or PowerPoint. Use File..Save as ..PDF to make the pdf file. (No Acrobat needed.)
• 'Print' the page or layout to a pdf driver (standard on the Mac print dialog; requires addon software for windows). 
• Draw boxes in two diagonally opposite corners of the page within Prism, then select them and make them white. Prism will include those drawings when it exports, so the exported image will fill a page.
• Put the graph onto a layout. Double click on that graph. On the dialog that comes up you can choose to crop. Enter negative values to add more white space (margin) around the graph.