OneDrive for Business allows you to share a link for a specific document with internal and external users to make collaboration easier. Anyone who has the link can access the document it points to and can view or edit the document depending on the permission level of the link.
Warning: Anyone on the internet who comes either across either a view only link or an edit link will be able to access the document in question with no login. If it's an edit link they will be able to edit the document with no login.
Go here for more information on how to share documents using Anonymous Guest Links
