You should be able to setup the 4500 for legal copying by first pressing the left or right arrow until you see "Copy B & W" for black and white; or "Copy Color" for color copies. Next press ok to select Copy Settings. Press the left or right arrow untill you find "Copy Paper Size" and press ok. Here you can select the size of the paper your copying. Select "Legal: for y our legal sized document. Now you should be able to press the Go button to scan your legal document.
Hope this helps!