Yeah, the term acid-free is essentially meaningless. Recycled products are (almost) never long-term archival quality. Always purchase through a reputable vendor that had a good reputation for working with cultural heritage institutions. You are looking for material like mentioned above and with a pH range that is 7.0-9.0, roughly. lignin-free and PAT tested (photographic activity test, but by no means are these materials just for photos- they have just been tested for refined non-reactive qualities) are better indications. Sorry office supply big box, you may be cheap-o, but you don’t have what we need.