The second method is the one that Pablo proposed. But this only copies the content of the Muffin Builder, not the whole portfolio, like the plugin does.
Just export the string, http://prntscr.com/nv9wcz and then import it on another page. It will copy the whole builder content.
Comments
You can import/export the page builder content with the import/export tool at the bottom of the builder, see screen: http://prntscr.com/h1emu4