Select All

To select it all, use Ctrl + A. This keyboard shortcut will do the exact same thing. Just click once on the page you want to copy, press Ctrl and A at the same time and poof, it's done!

Copy

You could use CTRL + C to copy and CTRL + V to paste it in the new location. You can also just hold the CTRL key and click-drag the item to copy it to a new location.