Install ATTACH EXTRA TOOLS, then right-click an attachment, 'Copy in the clipboard for new message', then in a Write window (new message), Attach/'Attachments from other messages'.

Thanks but,

This allows a copy into a write window, but I need to copy the entire attached file & past it somewhere else. Usually these are PDF files that need to go to a client folder.

If your client folders are Windows Explorer folders, just drag the attachment(s) from the message window and drop it in the Explorer folder. To save an attachment to a folder but delete it from the message, select the attachment, then right-click, Detach...