If you're copying an item that isn't the default size of 8.5" x 11", then you MUST specify the original size, which will determine the area the machine will scan...
From More Options, select Original Size and then choose which size option of the 14 given best matches the size of the original document. To help figure out the size, most of the size options are written around the top and left sides of the glass. So, for example, if the upper right corner of the document reaches "LTR-R" along the top of the glass and if the bottom left corner reaches "LTR-R" along the left side of the glass, then choose the "Letter-R" original size (which, by the way, just corresponds to an item that is 11" x 8.5", i.e., Letter-sized but Rotated).
Unfortunately, when you do this, the Paper Selection option defaults to whatever you choose for Original Size and demands you fill a tray with the correct paper size. To get around this, click on the Paper Selectionoption and choose a tray that the machine says is loaded with plain (8.5" x 11") paper. The copier will then automatically reduce/enlarge the Original Size to fit on the available paper. (Note: as a general policy we do not provide any size paper other than 8.5" x 11")