Most printer-paper you can buy in a shop is acid-free. I still have high-school printouts from 20 years ago that show no signs of degradation. I don't think any of my own digital assets have survived from 2003 — granted I was a teenager at the time, so I did not engage in the greatest archival practices. But see the comment above: all you need to preserve paper is to make sure it doesn't get damaged, and simply eyeballing it will confirm whether or not it has.