default
The default PageSpreadSlot to use for the first content document in publications if the publication does not define it. This option has no effect if the publication defines a SpreadSlot for the first content document, or when the activeRenderer cannot display spreads.
Possible values:
PageSpreadSlot.LEFT: The first content document of the publication will render into the left side in the spread.
PageSpreadSlot.RIGHT: The first content document of the publication will render into the right slot in the spread.
PageSpreadSlot.AUTO: Use PageSpreadSlot.RIGHT if PageProgressionDirection is LTR (left-to-right), otherwise use PageSpreadSlot.LEFT.