Before you make any big changes, make sure to make a backup of the page so you can go back to that version should anything go wrong.
1. Go to PAGES in the left navigation and click the edit GEAR icon next to the page you want to duplicate
2. In the window that pops up on the right, scroll down to the bottom and select DUPLICATE
3. Name the new page the same as the original, but add BACKUP and then the date
4. Move this page to the BACKUPS folder at the bottom of the NOT LINKS pages
5. Go back to the original version of the page and make your edits (Do not edit the backup by mistake)
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Both Squarespace and Localize provide great documentation and customer support on their websites. If there is something that you need help with that isn't listed in these instructions, you can check on their sites or contact support.