On any PDF review page, you can click and drag the slider at the bottom of the screen to enlarge or decrease the size of the document. As you enlarge the space, this will also give you more room to make more comments since the area in which to comment on the PDF increases.

You can also go right to the zoom percentage you want by clicking on the percentage number and selecting from our preset options. There are also options in the control bar to return the image to its actual size, or make it fit the screen.