By default, simplebooklet's are discoverable by search engines. You can hide your simplebooklet from all the major search engines from the Share Tab.
Go to the share tab and select SETTINGS.
Select Hide From Search Engines. Your booklet will now tell search engine crawlers not to index your content.
Hiding All Your Booklets (Paid Plan Feature)
Sometimes you want to hide all of your simplebooklets from search engines and only choose a few to be visible to crawlers. You can do this from the booklet settings button on your dashboard.
Tap the settings button just above your list of existing simplebooklets.
Go to the Search Engine tab.
Uncheck the green checkmark to flag all of your booklets to be hidden from search engines.