Please separate the lock/unlock function from the upload/download function. I don't necessarily want to download a copy of the drawing when I am locking it. Drawings are locked to prevent other users from "taking" drawings, but sometimes one needs to unlock the drawing in order to make necessary changes. It is good practice to lock the drawing again after the changes have been made.
Actually the best practice works the opposite. A released document is unlocked by default. To update the document a user (with edit rights) can start a workflow to update the document. The start of the workflow locks the document for the user. Once the update is done the user can release the document again.
Sorry. I was trying to use Internet Explorer earlier and it wouldn't let me leave a comment to clarify, so I edited my original request above.
Can you say a bit more about why you want to lock a document? E.g. a legal hold?