Abel can show you exactly what would be printed if you were to print the current contents of the blue line window, using the current Print Options and Page Setup. If you click the button on the toolbar, or click the File menu and then Print Preview, the Abel window is overlayed with one showing one or two pages of printout. A toolbar has buttons allowing you to move between pages of printing, and also letting you zoom in to see more detail of the page. If you put the mouse cursor over the printed page, it turns into a magnifying glass: clicking is another way to zoom in on a particular area of the page.
When you've finished looking at the preview, you can click the Print button to print it, or the Close button (or x on the window title bar, or press Escape) to return to the normal Abel window.