Some booklets contain content that is not appropriate for minors. To comply with the standards required by law in many countries, if your booklet contains adult content, you must add a permission gate to your simplebooklet. This will require the reader to accept that they understand the content is of adult in nature before they can view your booklet.
You can set this permission gate from the Share Tab, under settings.
Select Set As Adult Content.
You can remove this gate by selecting it a second time.