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        CHAPTER 10                                                       Document Interchange



        As shown in Table 10.46, the box color information dictionary contains an op-
        tional entry for each of the possible page boundaries other than the media box.
        The value of each entry is a box style dictionary, whose contents are shown in
        Table 10.47. If a given entry is absent, the viewer application should use its own
        current default settings instead.


10.10.2 Printer’s Marks

        Printer’s marks are graphic symbols or text added to a page to assist production
        personnel in identifying components of a multiple-plate job and maintaining
        consistent output during production. Examples commonly used in the printing
        industry include these:

        • Registration targets for aligning plates
        • Gray ramps and color bars for measuring colors and ink densities
        • Cut marks showing where the output medium is to be trimmed
        Although PDF producer applications traditionally include such marks in the con-
        tent stream of a document, they are logically separate from the content of the page
        itself and typically appear outside the boundaries (the crop box, trim box, and art
        box) defining the extent of that content (see Section 10.10.1, “Page Boundaries”).

        Printer’s mark annotations (PDF 1.4) provide a mechanism for incorporating
        printer’s marks into the PDF representation of a page, while keeping them sepa-
        rate from the actual page content. Each page in a PDF document may contain any
        number of such annotations, each of which represents a single printer’s mark.

        Note: Because printer’s marks typically fall outside the page’s content boundaries,
        each mark must be represented as a separate annotation. Otherwise—if, for exam-
        ple, the cut marks at the four corners of the page were defined in a single annota-
        tion—the annotation rectangle would encompass the entire contents of the page and
        could interfere with the user’s ability to select content or interact with other annota-
        tions on the page. Defining printer’s marks in separate annotations also facilitates
        the implementation of a drag-and-drop user interface for specifying them.

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