If you increase/decrease your page using the tools «Zoom in – Zoom out» (in the stylus bar) and then wish to the original dimension, you will find on the lower right of the page a button with a crossed magnifier.

If you click on it you will automatically return to the original size instead of using the opposite tool.

You can also make a double click on the “Zoom” tool that you have used to come back to the original display.