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SECTION 4.10                                                       Optional Content



level when viewing. Three groups (objects 1, 2, and 3) contain Zoom usage infor-
mation. Object 4 has none; therefore, it is not affected by zoom level changes. Ob-
ject 3 receives an OFF recommendation when exporting. When printing or
exporting, object 4 receives an ON recommendation.

Determining the State of Optional Content Groups

This section summarizes the rules by which applications make use of the config-
uration and usage application dictionaries to set the state of optional content
groups. For purposes of this discussion, it is useful to distinguish the following
types of applications:
• Viewer applications, such as Acrobat, which allow users to interact with the
  document in various ways.
• Design applications, which offer layering features for collecting groups of
  graphics together and selectively hiding or viewing them.
  Note: The following rules are not meant to apply to design applications; they may
  manage their states in an entirely different manner if they choose.
• Aggregating applications, which import PDF files as graphics.
• Printing applications, which print PDF files.
When a document is first opened, its optional content groups are assigned a state
based on the D (default) configuration dictionary in the OCProperties dictionary:

1. The value of BaseState is applied to all the groups.
2. The groups listed in either the ON or OFF array (depending on which one is
   opposite to BaseState) have their states adjusted.

This state is the recommended state for printing and aggregating applications,
which should not apply the changes based on usage application dictionaries de-
scribed below. However, for more advanced functionality, they may provide user
control for manipulating the individual states of optional content groups.

Note: Viewer applications should also provide users with an option to view docu-
ments in this state (that is, to disable the automatic adjustments discussed below).
This option permits an accurate preview of the content as it will appear when placed
into an aggregating application or sent to a stand-alone printing system.

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