The Prt Scr function is not the best way to do it! This is a hangover-from previous generations of the operating system and should only be used as a last resort.
Is your tree entirely Ancestry based? Do you have any genealogy software (such as
Family Tree Maker)? Most packages allow you to a do a *full* printout of your tree in a variety of different layouts. There are a few 'freebies' around also.
Unfortunately, DIY printouts of large family trees are rarely the best option. You will simply get lots of A4 sheets of paper which you then need to stick together to make a readable tree! But they are cheap.
There are several companies who will make a professional printout of your tree on one big sheet, but at a price!!! Take a look via Google.