Displaying a large and complicated family tree at once is not always possible. Generally speaking, you can always display the ancestors and descendents of any person on the tree, and you can usually display that same information for any siblings of that person.
You can often get what you want, by thoughtfully choosing the person to click on, and changing the options for how many generations of Parents, Children, and Others to show (under the show options link at the bottom of the screen). For instance, if you wanted to show the ancestors of both you and your wife, you could click on your child.
When I printed my family tree, I ended up printing it a couple of ways and using a layout program to combine them. In my case, I think I could have made everyone appear on the same tree, but It would have been annoyingly tall, and wider than the maximum width of a PDF file (which is approximately 17 feet).
