The short answer is: Word is not a good choice for what you're trying to do.
You can do all the bits of the task (selecting paragraphs, showing and
hiding, etc); but the mechanism ultimately relies on the structure of the
document, and as soon as you let people edit the document, you can't rely on
the structure remaining stable.

The best you can do is define bookmarks for the selectable paragraphs or
sections; then set the unselected matter to Hidden, either directly through
the Font object, or by applying a style.

There's no way show/hide pages in Word. Pages are not part of the document
structure as such (and don't figure in the object model) -- they are an
output of the document rendering, according to visible content, printer,
etc.

Another approach is to store your pages and paragraphs separately in a
database, then use Word to construct your output using only the selected
material. There are commercial applications around already that do precisely
that.