Word does not really recognise "Pages", only content (ie text, images,
tables) that happen to spread across several pages according to your page
setup settings. So you cannot select a "Page".
But saying that, you can use the Outline view to view the Headings, etc. So
long as you have used the Outline levels for your headings this can be very
easy and quick.

Say if you want to move section 4.2 to become the new section 2.3.
Outline View, set Show Level to "Show level 2", select 4.2, then use the
move up arrow til 4.2 becomes 2.3. This ensures that everything in Section
4.2 (including all sub-headings, tables, images, etc.) move in-toto. Also all
heading numbers are automatically refreshed.

If you have not used Outline Levels, Outline View can still assist in your
exercise, as it does show the page break you may have manually inserted (if
you are showing the non-printing characters). Just select waht you want moved
(ie a "page") and use the Move Up or Move Down arrows.

I suggest you try this in a copy of your document, just in case ;-)
Hope this helps
DeanH