Your source document page size must match the project's format size. For example, if you upload an 8.5 x 11 document then select 6 x 9 as the book size, Lulu scales your document to approximately 75% of the original size. The printed book will have unexpectedly small fonts and images. For more information about available book sizes, please see "What paper will my book have for the cover and interior?".
POD printers tend to print landscape pages sideways, so even if you are creating a wide format book (9 x 7), the uploaded source document page orientation must be set to Portrait, with page dimensions defined with the wider width than height.
If your uploaded source document contains unusual fonts, your book won't look like you expected. Use fonts that are readily available (almost anything provided by default in Microsoft® Windows® works). If you have unique or hard-to-find fonts in your document, provide a print-ready PDF of your work instead, making sure it meets our requirements — in particular, that the PDF includes the embedded fonts. For more information about PDFs and fonts, see "How do I embed fonts in a PDF?"
Always embed any images or other graphics that you use rather than linking (or referring) to them. When you save the document, an embedded graphic is part of the document file. When you save a document with a linked graphic, the document file only contains a pointer to the graphic file, and the document file and graphic file remain separate. When you upload the document to Lulu, linked graphics do not upload.
You can upload more than one file for a book. Lulu assembles the files in the order you specify and builds the final PDF. Drag and drop the files to arrange them into the order you want. Conversion does not change or update page numbering. Here are tips for using multiple source files for your project.
See also: What types of files can I upload?

