Is that still a problem for Lulu or apple, What exatly is the problems with Preview's "Print to PDF" option?
The only issue I am aware of with PDFs and Lulu are with manuscripts created using Pages and saved as PDF.
If you are converting from MS Word, there should be no problem. Just make sure the PDF is gererated at the same size as the book being created.
Upload and test it. If there is anything wrong you will be notified.