There are a number of ways to enlarge the Ftax form:
Firstly, by clicking on the bookmarks tab you remove the bookmark sidebar which will enlarge your screen:
Clicking the bookmark tab a second time will reintroduce the bookmark sidebar, reducing the size of the screen.
There are also 'zoom in' and 'zoom out' buttons. These are located on the first page of each section:
Finally, pressing F8 on your keyboard displays the toolbar. From here you can access the enhanced Adobe zoom features: