Get your journalist to follow you. Take them up to a bookshelf and tell them to "Use". Repeat this many times. Eventually you will have increase their Intelligence. This also works with everyone in the game. Just like how you can raise your photographers and writers intellect by making them follow you and telling them to use bookshelves, you can also do for Hef. His intelligence will also rise, but it sometimes will not work for the different bookshelves.