delete a document

You use the Finder to drag and drop a Pages document to the Trash. You would have a Time Machine or some other form of backup for the document in question beforehand.

If you meant to delete a page in Pages, and not a document itself, then that would depend on the type of Pages document, that the document was saved, and that aforementioned backup of the document exists:

• default word processing document
  • the page cannot be removed via the thumbnail, and all content on the page must be selected and removed including the preceding page break.
• page layout document
  • every page is its own section and you can right-click on the specific page thumbnail and choose delete