One way is to divide the document into sections. Please see:
http://word.mvps.org/FAQs/Formatting/NumberingFrontMatter.htm
But you cannot control the number of pages in a particular section; it
depends on the amount of text in the main body of that section.
Therefore, if you really mean that you want headers and footers to
start at a particular *page number*, you'll have to use a conditional
field in the header and footer.
A conditional field uses an IF construct to check the page number (as
determined by the start value in the Page Numbers dialog box) and
inserts contents based on the result. For example, the following
(nested) field, inserted in a header or footer:
{ IF { PAGE } < 4 "Text for pages 1 through 3" "Text for page 4 and
later" }
would display "Text for pages 1 through 3" on page 1 through 3, and
"Text for page 4 and later" on subsequent pages. If you change the
starting page number for a document (or section) that will affect the
result of the field. For example, if you set the starting number to 4,
you'll only see "Text for page 4 and later".
If you want all headers (footers) for the first three pages to be
blank (as indicated by the subject line of this thread), you can use
"" instead of "Text for pages 1 through 3" in the above field code
example, or you can use the following field instead:
{ IF { PAGE } > 3 "Contents here" }
Again, the actual number of pages whose header (footer) are blank
depend on the starting page number for the section.
Note that you cannot insert field delimiters, { }, by typing them from
the keyboard. Instead, you have to use CTRL+F9. In the above examples,
this means you would first position the cursor in the header (or
footer) area, then press CTRL+F9, type IF, then type CTRL+F9
again, and type the rest of the field code.
When you have typed the field code, press F9 to update the result of
the field. Alternatively, changing to Print Preview should display the
correct field results.
In order to toggle display of field codes for the entire document, use
ALT+F9. To do the same for the field containing the insertion point,
use SHIFT+F9.
For general information about page numbering and some more examples of
field codes in headers and footers, please see:
http://www.word.mvps.org/faqs/numbering/PageNumbering.htm