Here's how to do it:
1. Create a new document, type the desired text in the header.
2. Put your cursor in the body of the first page, insert a new section break (Insert > Section Break).
3. Your cursor will now be at page 2 of the document, which you'll see the header from first page that you created just now.
4. In the Layout Inspector, under Section tab, uncheck "Use previous headers & footers" checkbox.
5. After you uncheck, you will still see the header. Now select the header in page 2, and press Delete and you'll have an empty header for page 2, with the original first page header intact.
Note: the "Use previous..." option will only greyed out if you insert "Page Break", "Layout Break" or "Column Break"; or if your cursor is in the body of the first page. It will be activated if you insert a "Section Break" and put your cursor in the second (and subsequent) section.