If I understand correctly your requirement, you need both an image and some text as watermark in your pages.
Background tab of the page style dialog allows only one graphic to be inserted, you must edit your .png graphic in some external program (e.g. The Gimp under Linux) to include your text watermark in it.
The watermark, as a background, is a static component of the page style. When parts of the document receive different watermarks, these parts must have their own page styles. The easiest way to do this is to tune Default Style page style for “geometry” (margins, header, footer), then to create derived page styles where you add the specific backgrounds.
To switch from one page style to another, add a page break before to the first paragraph of the new page and set the desired page style.
Note: defining new pages styles is done through the
Styles & Formatting or
F11 side pane, clicking on the fourth icon ( Page Styles ) in the tool bar. You are encouraged to read the chapter(s) on style in the user guide if you haven’t done so.
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