So that was Hanwag's advice. However, comparable manufacturers such as Lowa and Meindl don't object to using newspaper when you want to dry your shoes. The Lowa UK team says:
USING NEWSPAPER OR KITCHEN ROLL
If you have either of these materials available, stuffing your boots with these is ideal for soaking up any excess moisture. For newspaper, removing sheets and rolling up into small balls is the best way to stuff your boots. The rolls should be reasonably loose as if they are too tight water may not be absorbed effectively. Another tip is to tear holes through the newspaper before scrunching. Place the paper or kitchen roll throughout the boot, all the way up into the leg opening. Again, make sure not to stuff too tightly as the paper needs a bit of space to soak the water. You can replace the kitchen roll or newspaper after a few hours to remove the first load of moisture before sleeping, or as many times as needed when the materials have been soaked.
I've used newspaper to no ill effect. As someone else said already, newspaper is not easy to come by on the Camino though. During one particular rainy period in Galicia, we tried to buy a newspaper in a shop during the day but even that was not always as easy as it may sound.