It is only possible to disable the share button for your publications if you are a PREMIUM or PLATINUM user. If you have a BASIC account and wish to benefit from this feature, please upgrade.
To deactivate this option, go to the Publications page of your account.
Select a publication and click on the Pencil icon.
In the window that opens, under the Sharing tab you will find the options for displaying the sharing menu for your document.
Click PUBLISH when you are finished.
If you wish to remove the sharing icon from the viewer, you will need to create a custom Skin.
You can learn more about how to customize your viewer here.