The transport mechanism really depends on the server interface, but since you are going through these options I assume you need to implement the server interface as well.
If you need to transfer the whole Word document as such, use File Transfer Protocol (FTP) or direct TCP socket-connection.
If you need the data from the Word document, you can serialize it in a machine-readable format, for example XML, and send it to the server using Hyper-Text Transfer Protocol (HTTP), for it's simplicity.
XML-RPC and SOAP might be too heavy and perhaps on the wrong abstraction level for your problem.
Oh, and for the client side: pick your client-side development tools after choosing your transport mechanism. Some languages and frameworks work better for different tasks than others.