This class represents the viewer preferences dictionary. This is definitively detailed in:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 150, page 362.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 147, page 435.

Adobe Supplement to the ISO 32000, BaseVersion: 1.7, ExtensionLevel: 3; Table: 8.1, page 28.

System.Object
    WebSupergoo.ABCpdf14.Elements.Element
       WebSupergoo.ABCpdf14.Elements.ViewerPreferencesElement

A viewer preferences dictionary allows a PDF file to specify how a conforming viewer should present it when first opened. The settings cover window layout, user-interface chrome visibility, printing behaviour, and page navigation direction.

All entries are optional; any viewer is free to ignore entries it does not support. The dictionary supplements the open-action and page-mode settings in the document catalog, which control a different layer of display behaviour.

The print-related entries - duplex mode, page range, number of copies, and tray selection - are advisory. A viewer that does not expose direct printing access may ignore them, and a user can override them at print time.

The Enforce entry limits which viewer-preference entries a viewer must honour regardless of user override. In current practice only PrintScaling can be enforced, and only by viewers that explicitly support the enforcement mechanism.

The area and clip entries - ViewArea, ViewClip, PrintArea, and PrintClip - specify which bounding box defines the visible and printable region. Omitting them is equivalent to specifying CropBox, the most common choice.