How to transfer numbers docs from lion on 2006 iMac to mountain lion on another computer (MBA)
Wouldn't this be the same as sharing any other document?

In Numbers, hold down the command (⌘) key and click the proxy icon in the title bar. Clicking the name of the folder that appears in the list immediately under the file name will reveal your document in the Finder.

Then, using the Finder, you could transfer the document using File Sharing, a USB drive, as an attachment to an e-mail.