The document text, minus the text boxes, is now in the new document. In the list of formats, choose Unformatted Text.Word displays the Paste Special dialog box. Choose Paste Special from the Edit menu.
One potential solution is a 'brute force' method. What if there are 30, 40, or more text boxes, though? Deleting them individually can quickly get tedious. If there are only one or two text boxes in the document, it is not that difficult to select them and delete them. If you do a lot of work with documents from other people, you may have a need to remove text boxes in those documents.