The footer area in "Teste footnote.docx" contains only a single paragraph end mark (a single empty paragraph). The page number is placed in a text box located partly outside the footer area. That text box is itself anchored to the empty paragraph in the footer. This is a most unusual setup for a Word document. You’d be better off doing as follows:
1. Select the text box and press the Del key to remove it with the page number.
2. Press the Del key again to remove the paragraph end mark associated with the "[Basic Paragraph]" style.
3. Insert the page number in the standard usual way in MS Word.
4. If need be, adjust the position of the page number and the size of the footer area.
HTH.