This website splits documents into four broad categories of canonicity:
Canonical documents have been confirmed to be true in the Elite: Dangerous universe.
Guideline documents weigh heavily on the minds of people building the Elite: Dangerous canon, but are not guaranteed to be true. Much of the canon from the Frontier games falls into this category
Inspiration documents are probably known to the people building the Elite: Dangerous canon, and may impact their decisions
Mixed documents embellish real information in confusing ways. Many dreamers have made the Frontier universe a happy home, but be careful not to mistake these pages for facts.
Speculation documents could influence the people building the Elite: Dangerous canon, but they have absolutely no obligations.