how do i display/protect the ketubah at the wedding?

To display at the wedding, ask the caterer for an easel. many people put it where the place cards are so everyone can see it but it's out of the way.

an easy way to back and protect the ketubah: get a piece of thin foamcore, which you can buy at any art supply store, and cut to the same size as the ketubah. Tape the ketubah to it using masking tape loops in each corner in the back of the ketubah.

Cut a piece of very thin clear plastic, that you can also get at an art supply shop, to the same size as the foamcore, lay over the foamcore and using clear tape, tape along the top like a hinge. This will protect the ketubah at the reception and allow you to sign it by lifting the plastic. after signing, tape along the bottom as well.

there is a handy downloadable sheet with all this info in the care section.