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.
The portion of the tree displayed on the screen will always be the portion printed when you choose print.