1. A method for merging document metadata at a client computer, the method comprising: obtaining a document from a server computer at the client computer, the document being requested by a user at the client computer; opening the document at the client computer; in response to opening the document at the client computer, determining whether the document includes unit identifiers; when it is determined that the document does not include unit identifiers, assigning a unit identifier to each unit in the document; receiving a first message from the server computer providing notification that at least one other user is authoring the document; in response to receiving the first message from the server computer that at least one other user is authoring the document, sending a second message to the server computer, the second message including first metadata for the document; in response to sending the second message to the server computer, receiving a third message from the server computer, the third message including second metadata for the document; in response to receiving the third message from the server computer, determining whether the first metadata and the second metadata should be merged; and when it is determined that the first metadata and the second metadata should be merged, adjusting unit identifiers in the document based on the second metadata.