The script attached to this article should be downloaded and installed in your Photoshop Scripts folder. This can be used to cut your full spread designs into two pages, left and right. The script will also save out these individual pages with sequential file names for easy order upload.
Please note that this script will only work successfully if your original spreads are sized correctly. To download the PSD sizing guides that show specific sizing for each book, click the link below.
ProDPI Sizing Guides - https://www.prodpi.com/download/