Temporary lock file created by LibreOffice, a free office productivity suite based on the OpenOffice.org source code; created when editing a saved document (.DOC file) and deleted when the document is closed in LibreOffice; used for locking the document from concurrent use.
DOC# files use the filename convention .~lock.MyDocument.doc#, where "MyDocument" is the name of the document being edited. The DOC# file is created in the same directory as the DOC file being edited.
Temporary lock files are also created for other file types being edited in LibreOffice. For example, an ".odt#" file is created when editing an .ODT document.
NOTE: DOC# files are saved in a plain text format and include the current user opening the document, a timestamp when the document was last saved, and the location of the LibreOffice lock information directory ([user]\AppData\Roaming\LibreOffice\3\ in Windows).