i am writing a book that has images and photos in it. i will publish with createspace and they require i give them a pdf.

of course i want the pictures to show as good as possible.

which file format is best to use, jpg or png?

i will first insert these into the word document, then convert that word document to pdf and then they will print this pdf on white paper.

so which file format is best for the things described above?

any other suggestions to improve this situation?