How can/do you preserve old newspapers?

The library of Congress has some information online regarding the proper care of your newspaper collection :

http://www.loc.gov/preservation/care/newspap.html

As far as display, that’s probably not a good idea. Light exposure isn’t recommended.

If you’re going to display them, be sure they are framed with all acid-free materials and covered in UV protectant glass. A good, reputable archival frame shop is what you need.

Even so, display them away from direct sunlight.

I agree go to a frame shop and tell them what you want to do. They should know what to do. If the person helping you immediately starts talking fram lingo and preservation I think you are good. If he umms a lot and kind of throws out not very confident suggestions of what you could do, go to the next place. I would guess acid free, UV protection, and air tight is the way to go.

If you have a local museum you could ask them about a local framer who they use. Or, someone at the art or photography department at a local university.

And see that fumigation is part of the preservation process.