A page border is used to group all the layout elements of a print map together by means of a single graphic line surrounding all of the elements. When the layout consists of a single map element with all other elements floating on top of the map, the page border is sometimes, but not always, redundant with the map border. When the layout contains elements outside of the map element(s), a page border is usually used to contain those items.
Placement: The page border is placed around all the layout elements, including a narrow white-space buffer that acts as a frame. The frame does not have to be white; it can be any color that unifies the layout. The frame ought to be the same width or proportional to the other separating spaces on the layout.
Style: Double lines, single lines, varying thicknesses, shadow boxes, rounded corners, and so on are all used and acceptable. The simplest and best is the single line page border so as not to detract from the surrounding elements. Just make sure that poster-sized maps at C size or larger that have page borders that are of at least 3-point thickness, and up to 5-point thickness for E size sheets.