Use the latex-based (not oil-based) Sizing for Gold Leaf - easily found at any good art supplies store. It sits on top of the paper so no damage will be done to the paper. It dries tacky in about 5 minutes, that's when it's time to apply the leaf. (Read instructions on the bottle).

There's no reason you can't use acrylic medium underneath the leaf... I would use matte so it doesn't look so different from the surface of the paper.