Yes, you can. From the Site Center, here's how:
Clicking the Update SLS2 button will present you with a list of pages than have changed since the last conversion. Use the links for SLS1 and SLS2 to view and compare the old and new pages. Check the box next to all the pages you wish to re-convert and then click the Update button.
Q: Do I need to update news and events?
A: No. News and events update automatically so there's no need to worry about updating those manually.
Q: Will updating pages replace changes I made on the new site?
A: Yes. The re-converted pages will replace the new page. For that reason, we allow you to re-convert selected pages rather than re-converting an entire site.