Sorry, I had "acid-free" sheet protectors on my mind from another project. I use standard plastic sheet protectors that you can buy at Office Depot or Office Max.

The reason I keep hard-copies is because it cost me money in the first place to get (either from the County Clerk or online from Ancestry when I had a subscription).

I am a self-proclaimed hoarder of family history items, so it may be overkill.