Text boxes can be resized to accomodate text that is larger than the original box. Try grabbing the text box handles with the Select tool to resize, or right-click and choose ‘Fit To Text’ from the contextual menu. – Jill
This can sometimes happen with italicized text because the internal text metrics don’t take that extra needed space into account. Try right-clicking on the text box and unchecking ‘Clip Contents’ – this will allow the text to render beyond the strict bounds of the text box and should solve the problem.