Can anybody help me on how to preserve a VERY cute charcoal drawing done for me of myself & my family?

Hi. Thank you to anybody that can help me with this. History: About 8 years ago when I was at a fair in Arlington, TX my husband, myself & my two adorable boys had a charcoal sketch done for us free of charge. It is known as a "Butt Sketch", meaning that it is sketched from the backside as opposed to the front side. Details: It's pretty large in size (approx. 18 x 24). Since it was done, I've just had it "preserved" in between 2 pieces of cardboard (collapsed moving box) & taped. The sketch itself is starting to smear & the paper (sketch paper, I assume) is starting to curl so I most definitely don't want to totally lose it. The Point: I can't afford to have it professionally "fixed". How do I "fix" it myself within a budget that works? Matte it, etc. Any help would be MOST appreciated!!!