The rule of thumb on framing is if it's worth framing, frame it to museum standards. What this basically means that anything that comes into contact with the art work won't cause any deteroration. Most paper is acidic. All fine prints and art work are produced on non-acidic paper. This acid causes the yellowing or browning which starts on the edges. Most mat board is acidic. Glues are a no-no.
If you have a piece of art framed, insist on "museum standards". and have the framer guarantee it. This means 100% rag, non acidic mat board. To hold the art work in place, special tape with non corrosive adhesive is used.
The cost between the wrong and right framing is nominal.