The Pages window has sidebars on the left and right of the document:
Click
in the toolbar, then choose Page Thumbnails or Comments & Changes.
Click
in the toolbar to show formatting controls for whatever is selected in the document, like text, a shape, or a chart.
Click
in the toolbar to show controls to format the document—set page orientation and size; set margins; and add headers, footers, and document sections.
Note: If a sidebar on the right is open and you click its icon in the toolbar, the sidebar closes.