This worked perfectly!! You saved me an incredible amount of time!! Thank You!!The methods I would employ for something like that
1. Crop off the bottom and right sides of all pages
2. using the plugin Quite Imposing, perform a "Tile Pages" operation: 2 Across, 4 Down
its not perfectly on the grey lines, but its the simplest way I see to do it. I don't know of anything that will auto-magically crop apart pages based on the position of a line