You can send attachments with your messages using either MIME or DIME. You need to find out which (if any) your SOAP implementation supports (and that of your customer!). Most implementations support MIME, although a growing number of implementations now also support DIME. MS SOAP and .NET only support DIME. Look through your product documentation. You should be able to find information on using attachments with your product. (It's handled differently by every product.) If your product doesn't provide documentation, try using Google to find some samples.
This was first published in January 2003