What specifically are you trying to accomplish? As @John Mensinger said, you can easily re-size the artboards as he showed. Because Illustrator is vector based, everything is easily scaleable, but when you change the artboard size it does not scale the art within it.
The artboard that John Mensinger refers to would be comparable to the Canvas size in Photoshop. Changing the size of the Artboard would not affect the size or dimensions of the actual layout. To do that you would use the Scale Tool. With all elements of the layout selected and then double-clicking on the Scale Tool you will get the Scale dialog Window. In that window you can enter percentages to enlarge or reduce the size of the selected layout either uniformly or in a non-uniform manner. The scaling will be done outwards or inwards from the center of the selected art. You'll also notice in the screenshot that there are options for scaling elements of the selected objects. You can also use the Scale Tool to manually enlarge or reduce the size of the layout. With the entire layout selected and the Scale Tool chosen click on a point of the layout that you want to enlarge or reduce from. This will anchor the layout at that chosen point. Then drag with the Tool from another point in the layout and pull outward to enlarge or inward to reduce the layout visually.