How to fix it? By pressing “Print Summary”, there are 2 extra blank pages printed
There is CSS that is adding the space. When I remove the height for the following it will not print blank pages.

crm-container div.form-item {
height: 100%;
}

I would create an "extras.css" so that you can override some of the built-in CSS. You can specify a custom CSS file under Administer > System Settings > Resource URLs: Custom CSS URL. 
Note: the path to the CSS file should be accessible from a web browser. 

If you add the following to the extras.css then it will fix the print of extra pages:

#Print1 div.form-item {
    height: 0;
}


When you go to print summary you can cancel the chrome printing pop-up and then inspect the CiviCRM page (it has the "print" and "done" buttons). You can further refine the print style using the Chrome Dev tools.