Each size and format of our photo books is its own product, so you won't be able to change sizes after personalizing. You will need to start over again from the size you want, but don't worry, your photos will be saved in the library within the photo book editor and with the Autofill feature it's easy to populate a new book with photos.
If you've already placed your order, you can cancel your order (How do I cancel my photo book?) to start over with a new photo book. Otherwise, you can simply delete the book from your cart.
Questions? Contact us and our support team will be happy to assist.