What is an appropriate size for a portfolio?

I work at a newspaper and have some full page ads which are about 11.5 x 22.5 in full size. How should I go about putting those in a portfolio? I'm wondering if its ok to fold in half (crease is already there when the newspaper is printed) but that would mean taking out of the sleeve to view the whole page. But to have a portfolio as tall as a newspaper seems cumbersome and maybe too big to bring to an interview. Any serious suggestions/advice welcome please!