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                                     CHAPTER 8


                     Interactive Features
                     8




    This chapter describes the PDF features that allow a user to interact with a docu-
    ment on the screen, using the mouse and keyboard (with the exception of multi-
    media features, which are described in Chapter 9, “Multimedia Features”):

    • Preference settings to control the way the document is presented on the screen
      (Section 8.1, “Viewer Preferences”)
    • Navigation facilities for moving through the document in a variety of ways
      (Sections 8.2, “Document-Level Navigation,” and 8.3, “Page-Level Navigation”)
    • Annotations for adding text notes, sounds, movies, and other ancillary infor-
      mation to the document (Section 8.4, “Annotations”)
    • Actions that can be triggered by specified events (Section 8.5, “Actions”)
    • Interactive forms for gathering information from the user (Section 8.6, “Interac-
      tive Forms”)
    • Digital signatures that authenticate the identity of a user and the validity of the
      document’s contents (Section 8.7, “Digital Signatures”)
    • Measurement properties that enable the display of real-world units correspond-
      ing to objects on a page (Section 8.8, “Measurement Properties”)


8.1 Viewer Preferences

    The ViewerPreferences entry in a document’s catalog (see Section 3.6.1, “Docu-
    ment Catalog”) designates a viewer preferences dictionary (PDF 1.2) controlling
    the way the document is to be presented on the screen or in print. If no such dic-
    tionary is specified, viewing and printing applications should behave in accor-
    dance with their own current user preference settings. Table 8.1 shows the
    contents of the viewer preferences dictionary.


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