Agile and efficient documentation update

I was wondering what are your experiences with companies that are making so many improvements to their processes that the documents that describe de process (procedures, process flow diagrams, etc.) just are not up to date? Is a dedicated group of people changing documents a solution? Should every manager update with his people the documents when changes are made?

Somewhere I read that in some Japanese manufacturing companies they used blackboards where they could easily erase and write the new SOP in order to keep it updated. Any experiences on this issue could be useful. Thanks.