Paragraph formatting?

I am new to adobe and just wrote a book using word and had to transfer to PDF for Amazon to publish.  My proof has any paragraph that would not fit on a page being moved to the next page thus leaving a big white space.  So If I had 15 lines before the end of a page and a 20 line paragraph it moves the whole paragraph rather than breaking it on the last line or even at a sentence.  How can I change the rule so the pdf formats more normally? Do I have to break it manually at each page?  Long book!