The 'keep with next' parameter, when applied to all paragraphs, as it is in your attachment, is essentially meaningless. It should only be used on paragraphs that do need to be kept on the same page as whatever follows (eg headings).

The widow/orphan control, as referred to by Cobb78, will have minimal effect (none on page 4, for example).

Regarding page 4, the main reason for the gap is that the first line on page 5 contains a footnote reference. Since Word can't fit both that line and its footnote on page 4, the line goes to page 5. If you were to move the footnote reference to a later line (and I'm not saying that this is appropriate here), then line could move up. Reorgnising the text, including, perhaps, adding more text between footnotes 21 & 21, could likewise result in less space at the bottom of the page. Deleting, say, footnote 20 would also achieve the same result. Ultimately, you'll have to decide when it's more important to have/not have (ie padding) some particular content than to worry about the page layout.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]