Splits pages in half in a certain direction (horizontally, vertically, or orientation dependent), based on the desired page box.
Orientation depending means that the landscape pages are split vertically and portrait pages are split horizontally.
This Action can be useful if you scanned two pages of a book as a single page, but want to have them as separate pages (e.g. for better readability); or if you have an image spread over two pages which has to be split in two for printing purposes.