This is why I now seal mine with a matte finish acrylic spray. If you get the matte finish spray, it's not too shiny and it seals with out streaking or discoloring the images. I mask off the metal clip with painters tape and use a cut away spray box and do a couple light coats. It takes minutes to dry and gives a beautiful finish. I agree that the backs should be done too because that's what people see if they actually use it as a clipboard! If it's hanging on a wall as a notes organizer then leave it blank.
This shows the light sheen from the acrylic spray:
my clippies
Have fun!