Textboard is a very simple and intuitive Tool for zooming texts. The entered text is zoomed in real time and can be adapted smoothly. You can control the entire app with your bluethooth keyboard. Therefore it is a perfect tool especially for this case and as white board.
Use Textboard e.g. for optical or teaching aid. The possible applications are infinite.

In the menu you can adjust settings.

Also available as Pro Version: https://www.google.com/url?q=https://play.google.com/store/apps/details?id=com.kewitschka.textboard