We've created this Forum Thread with some workarounds and advice to assist you in publishing you ebook.
Help! I am trying to make my book and when i upload my PDF, it keeps saying the image in my book is low resolution. The image is my drawing that I scanned on the printer to the computer.. I don't know how to make it a better resolution. I used printer scanner to change the DPI to 600 but Lulu still says it's low resolution. Can i just leave the photo or will it look bad in a book? it's not a crazy detailed photo, it's just a scibble with sharpie on white paper.
When i put the document on lulu, the preview of the drawings on the book look fine. So if it looks fine on the preview will it look that same way in printed book form? If so i'll just leave it that resolution