I never understand this 'they won't fold up' nonsense
I don't trace, but in any case, cut away the acres of excess paper around the sheets, separating the pieces. Fold them up, smoothing out as you go, then PRESS with an iron. Done. I've been using standard patterns for years, and they always go back in.
The awkward ones are the PDFs as all that printer paper [and sellotape or glue] can make an unholy mess. I use plastic document wallets for those, ordinary ones for putting in folders. Works well enough. I have a small filing cabinet [2 drawers] jammed full, plus the 'work in progress' drawer in my sewing room, and a few shoeboxes of 'not likely to be revisited'or 'old patterns for kids'
Recently, I bit the bullet and made a spreadsheet list of ALL of them, with marks for ones I'd made up. All sorted by pattern company. It helped me see what I really have, where there are duplicates, and what NOT to buy again!
Very informative.