welcome to the Pages Discussions. On which pages do you want to delete the headers/footers. Pages gives you the option to have different headers/footers on the first page then on the following pages of a section. That means you can have a header/footer on the first page but not on the following or vice versa. You can find the settings in the layout inspector under the tab button "section". There you can set "The first page is different" and "Use previous header and footer". Like the placement of this options tells, this settings are for sections.
But if you want to have different headers/footers in the middle of a section, you have to cover them like Magnus posted before. Or like John posted to insert new section breaks, but that breaks the text flow, too.
