OSHA HazCom, 29 CFR 1910.1200(g)(5) — when significant new hazard information comes to light, the SDS must be updated within three months. An audit asks two things: is the current sheet right, and can you show what it said before. Version history answers the second.
Automatic revision numbering — publishing a change increments the revision; no hand-managed "final_v3 (2).pdf".
Prior versions stay on file — review any superseded revision of a sheet you authored, with its date.
Frozen at publish — a published sheet renders from the snapshot taken when it was issued, stamped with the engine version that produced it.
Drift flagged — the library re-checks published sheets against the current engine and flags any whose classification would now differ; one click reopens it to refresh and re-publish.
Supplier sheets too — replace an uploaded supplier PDF and the old file stays under that sheet's previous versions; delete one and it moves to Archived SDSs. Each file is kept for 30 years, the retention OSHA sets for exposure records.
Included with every sheet you author — the $79 one-off covers it. Supplier-sheet history is included on every plan, Free onward.
Author with a real revision trail from the first sheet you publish.