What does Ubooquity need to correctly scan a PDF?

If I have a folder containing a single PDF. What else does Ubooquity need to scan/index it correctly? With Magazines I know it needs a cover scan jpg, but is there an index file that I could also provide, and if so what format does Uboo require? I don't use calibre, so not going there.

Can I do something like this?

>Book Folder

>>Book.pdf

>>Book.jpg

>>Book.idx ???