We've created this Forum Thread with some workarounds and advice to assist you in publishing you ebook.
Your document could not be created: We do not accept PDF documents with pages of differing sizes.
The above message has appeared at the uploading stage. I have checked the page sizes and they are all the same size.
I notice if i upload the word doc it accepts it ok. However when Lulu converts the word doc to pdf it changes some of the formatting which makes it uselss.