There are a few different ways that you can seal contact paper, depending on the type of material that you are using it for. If you are using contact paper to line drawers or shelves, you can simply use clear packing tape to secure the edges. If you are using contact paper for a craft project, you may want to use Mod Podge or another type of decoupage glue to seal it. You can also laminate contact paper with an adhesive-backed laminate sheet if you want a more durable finish.