From PDF XChange PDF SDK
The event is fired when the document's properties are being changed.
|The PXV_ChangeDocPropsFlag are specified here that indicate which properties were changed.
|Specifies whether the event was handled. Marking the event as handled will cause the event sender to look at the event`s result and act accordingly based on the event type.
|Specifies the result that will be used by the event sender when the event is marked as Handled.