By the way, Finder will let you get info on just about any document and check 'Locked' or 'Stationary Pad'. Locking should prompt you on any attempt to change

By the way, Finder will let you get info on just about any document and check 'Locked' or 'Stationary Pad'. Locking should prompt you on any attempt to change the document to unlock or duplicate. Stationary Pad will automatically create a local copy when you open the file, and instead open that copy.