PDF (adobe.com)

Protect layers and objects

Locking an individual object protects it by preventing it from being selected or edited, and locking a layer protects all objects on that layer. A padlock icon  indicates a locked item. The Single Layer Editing feature protects objects on all but the active layer and sub layers from unwanted selection or changes. You can also protect objects and layers by hiding them.

Note: Hidden layers and objects are not included when you export a document. Objects on the Web Layer can always be exported, whether or not they are hidden. For more information about exporting, see Export from the workspace.