Header text and numbering

Ignore the fancy header and footer and page number building blocks (the problem is that they are mutually exclusive). Instead, double-click in the header area to access the header. Type the text you want at the left margin, tab twice to get to the right margin, and press Alt+Shift+P to insert a PAGE field.           

And in future, if you need to use one of the built-in header/footer building blocks and add a page number, use the Current Position setting on the Page Number menu; this will insert a simple page number rather than a Page Number building block.

Paul,

Using one of the built-in numbering blocks you will erase everything that is in the header. Instead in the header, type the text in the left hand corner, position the cursor by pressing Tab-key. Then put your page number in, use Insert - Page numbers - Current position - choose the plain numbering item. Or if you want you can add the page number yourself, just press Ctrl+F9, type PAGE between the brackets, press F9.