In EAGLE, to see individual layers, click the "Layers" button (looks like red green and blue squares stacked) near the top of the tools bar along the left side of the screen. Turn off blue to see the red layer, etc.
http://www.seeedstudio.com/depot/datasheet/seeeduino.brd
If you want a schematic, search for the *.sch file instead of the *.brd file. This will also open in Eagle, and give a logical view of the design, rather than a physical view of the design.