The document is locked for editing by another user

If you try to open a shared document, you may be greeted with the message "The document is locked for editing by another user".  If the file is not actually in use by "another user", this behaviour may occur if the Office application previously quit improperly and, therefore, did not delete the "owner file".

The solution can be to delete the "owner file"

• Start by checking that "another user" do not have the document open
• Close the Office application in which the file was created
• Open the document folder where the locked file is located
• The "owner file" will be in the same folder as the locked file, where the name will begin with a tilde and followed by the document name, e.g. "~ filename.doc"
• If you can't see it right away, choose show -> hidden items
• Delte the file name that starts with a tilde "~filename.doc" 
• You will then be able to open the document

For further information see here