PDF without the watermark

I am making a book for my grandfather's history. It will be 400 pages and we will be printing at least 20 copies of this book. I know I can save it as a pdf on my computer, but then I have a watermark on it. My concern is this: in 20 years when the great grandchildren want a book of grandpa's history--blurb won't be in business and I will be out of luck. I have no problem (largely because it is grandpa's money) using blurb to print my books. However, when I spend my couple of thousand dollars and have my book, I want the pdf of my book without a watermark for future use. Can I get that from you?