FYI, A watermark object (picture or text) is
anchored in the Header area.
You can use different watermarks on Different pages as:
1. Make sure that you use section breaks to separate
the sets of pages that require differing Watermarks
(including sections with NO watermark). for this go Page layout ----Page setup ---- Break ---- Section Break
2. Insert the Watermark you would like for any section
- initially it will be the same throughout the document.
3. Double-click, and modify, the Headers so that each
section does NOT have 'Same as previous'.
4. Move to the (in your case) first section, double-click its
Header - you will now be able to 'select' the watermark
with a single (Left-)click.
5. Right Click the Watermark, choose 'Edit text,
and modify the Watermark for that section.
6. Repeat for the other sections until you have whatever
Watermark you want (including NO Watermark) in each