PageMarginBox:
| "top-left-corner"
| "top-left"
| "top-center"
| "top-right"
| "top-right-corner"
| "left-top"
| "left-middle"
| "left-bottom"
| "right-top"
| "right-middle"
| "right-bottom"
| "bottom-left-corner"
| "bottom-left"
| "bottom-center"
| "bottom-right"
| "bottom-right-corner"
A page margin box.