Once the text box is in the document, it's treated as an image — you can resize the box by clicking and holding on its corners, but the dimensions of the letters within may get warped.

Did you know that you can insert Picture in Word without moving Text? Learn how to add image in SmartArt text & then wrap text.

Learn how to delete a text box without removing text in Word or Excel using Format Shape pane, setting the text box to No Outline, and more.