Archival, acid-free paper is a high-quality paper designed to resist deterioration, yellowing, and brittleness over time. Pretty much all modern commercial drawing papers available for purchase today will be acid-free. This type of paper is manufactured to have a neutral pH of around 7, achieved by processing the wood pulp or cotton fibers to remove the lignin component that makes pulp acidic. If the lignin wasn't removed during processing, the paper would become brittle and yellow with age, as seen in old book paper.
Cotton-based archival papers are often considered superior to those made from wood pulp, as cotton fibers are longer, stronger, and naturally acid-free. Acid-free paper is archival because it won't degrade over time, making it suitable for displaying artwork for years without the materials changing in appearance. This is in contrast to non-acid-free paper, such as old book paper, which discolors and becomes unsuitable for art applications over time.
To ensure the long-term preservation of your artwork, it's essential to use reputable, artist-grade paper for the drawings you want to keep, instead of drawing your masterpieces on any old copy paper or scraps. When selecting paper for your art, simply read the product description on the art supplier's website, which will usually indicate whether the paper is acid-free and of archival quality. By choosing archival, acid-free paper, you can confidently display and preserve your artwork without worrying about the paper deteriorating, discoloring, or damaging your creations.