
The ArtBox can be used to indicate the dimensions of this part of the page. The area where it is safe to place graphic elements is called the safety zone or text safe area. In book design, there is also a margin where you cannot put text because the binding might make it difficult to read text that is too close to the spine. If the poster is not mounted properly, this could cause that text or logo to disappear behind the frame of the lightbox. When creating a poster that will be placed in a lightbox, the designer must make sure text and logos aren’t positioned too close to the edge.
#Adobe acrobat not cropping for final print pdf
This allows you to place that PDF on another page but only use the area covered by the advert. On a PDF page that contains an advertisement, the ArtBox can be used to define the location of that ad.It is never used for that but can be handy in a few cases:

It was originally added to indicate the area covered by the artwork of the page.

For prepress use, this is not the case as we prefer our pages to be defined slightly oversized so that we can see the bleed (Images or other elements touching an outer edge of a printed page need to extend beyond the edge of the paper to compensate for inaccuracies in trimming the page), the crop marks and useful information such as the file name or the date and time when the file was created. For the average user, this probably equals the actual page size. The MediaBox is used to specify the width and height of the page.These are called the boundary boxes or page boxes:

There can in fact be up to 5 different definitions in a PDF that relate to the size of its pages. That page size definition is not as straightforward as you might think. It also contains a definition of the physical size of those pages. A PDF describes the content and appearance of one or more pages.
