If you know that a PDF of the book is available, then you can ask "Can I have the PDF of the book?" If not, it would be better to ask "Can I have the book in PDF format?"
Strictly speaking, since the "F" in "PDF" stands for format, "PDF format" is wrong, but it is commonly used. You could always ask instead "Can I have the book as a PDF?" or "...as a PDF file?"