Every magazine is public by default after it has been created and can be found in the Yumpu search or other search engines. To limit or forbid this you can use the so called "Visibility settings".
You find those settings for your magazine under "My publications".
Scroll to the "Visibility Settings" and choose the visibility you desire.
There are 9 different privacy options:
Everybode can read and find your magazine.
Only through direct link:
Only readers that know the link to your magazine can find it. It won't show up in the search.
Protected on yumpu with password protection:
To enter the magazine the reader must enter a password. It won't show up in the search.
Protected on Yumpu with secret link protection:
Works similar to the direct link, but the automatically generated link of the magazine won't work. Only a secret link, known to the author, can be used to access the magazine. This is important for example if your magazine was public first and the official link to the magazine is already known to many persons. It won't show up in the search.
Only on my website allowed:
The magazine can only be embedded on specific domains and can only be read on those domains. It won't show up in the search.
Only in my WEBKiosk allowed:
The magazine can only be read in a specific WEBKiosk.
Only in my APPKiosk allowed:
The magazine can only be read in your APPKiosk.
Only in my WEBKiosk and APPKiosk allowed
Both options combined
Only the logged in author can read the magazine.