Working with the attachmentWrapper Object
Once you have an attachmentWrapper, you can get the attachment's metadata as described in the record pub.ariba.supplier.attachment:AttachmentInfo, or you can get the attachment's contents in bytes.
To get the attachment metadata information, invoke the service
pub.ariba.supplier.attachment:getInfoFromWrapper.
To get the attachment's contents, invoke the service
pub.ariba.supplier.attachment:getContentFromWrapper.
Set the format input parameter to bytes if you want the contents in bytes, or set it to string if you want the contents in string format.