What do status, freshness and “Canonical” mean for a document?

The status is “Draft”, “In review”, “Approved” or “Published”. Under “Freshness”, you set how often the document should be reviewed (every 30 days, every quarter, every six months, yearly or never); when it's due, it appears on the home page under “Review due”. “Canonical” makes a document the preferred source: it's found first and warns about duplicates. Only the owner can set that.