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                                        965
SECTION 10.10                                                      Prepress Support



  the applicable usage conventions, the placed content may be clipped to either
  the art box or the bleed box. (For example, a quarter-page advertisement to be
  placed on a magazine page might be clipped to the art box on the two sides of
  the ad that face into the middle of the page and to the bleed box on the two
  sides that bleed over the edge of the page.) The media box and trim box are
  ignored.
• Printing a finished page. This case is typical of desktop or shared page printers,
  in which the page content is positioned directly on the final output medium.
  The art box and bleed box are ignored. The media box may be used as advice
  for selecting media of the appropriate size. The crop box and trim box, if
  present, should be the same as the media box. (See implementation note 167 in
  Appendix H.)
• Printing an intermediate page for use in a prepress process. The art box is
  ignored. The bleed box defines the boundary of the content to be imaged. The
  trim box specifies the positioning of the content on the medium; it may also be
  used to generate cut or fold marks outside the bleed box. Content falling within
  the media box but outside the bleed box may or may not be imaged, depending
  on the specific production process being used.
• Building an imposition of multiple pages on a press sheet. The art box is ignored.
  The bleed box defines the clipping boundary of the content to be imaged; con-
  tent outside the bleed box is ignored. The trim box specifies the positioning of
  the page’s content within the imposition. Cut and fold marks are typically gen-
  erated for the imposition as a whole.

In the scenarios above, an application that interprets the bleed, trim, and art
boxes for some purpose typically alters the crop box so as to impose the clipping
that those boxes prescribe.


Display of Page Boundaries

For the user’s convenience, viewer applications may offer the ability to display
guidelines on the screen for the various page boundaries. The optional BoxCol-
orInfo entry in a page object (see “Page Objects” on page 144) holds a box color
information dictionary (PDF 1.4) specifying the colors and other visual character-
istics to be used for such display. Viewer applications typically provide a user in-
terface to allow the user to set these characteristics interactively. Note that this
information is page-specific and can vary from one page to another.

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