Delete a page in a page layout document: Click in the toolbar, then choose Page Thumbnails. Select any page in the section you want to delete (a background color appears behind all the pages in the same section), then press Delete on your keyboard.
Delete only a portion of a page or section: Copy or cut the content you want to keep, paste it somewhere else (a different page or section), then delete the original page or section as described above. Alternatively, you could Undo or redo changes in Pages on Mac