From the web:
WP can shrink ANY size document to the specific number of pages,
giving YOU the option of what to reduce, e.g., Font, Spacing, Margins,
etc. Additionally, only WP gives you the option of 'Block Make It
Fit', which lets you adjust a specific number of pages within your
document.
I read some where that Word can reduce your document by 1 page, and
you have no say in what it will change to make it fit but I have been
unable to find this feature.