Using Layers
If a PDF file has been created with layers (optional content), you can use the layers user interface to toggle the visibility of the presented layers.
Layers are displayed on a tab in the utility pane on the left side of the Viewer. However, they are not displayed if View > Hide Utility Pane has been selected.
The layers pane will list all optional content encoded in the document with a label and checkbox to control visibility. Some documents will be encoded to only allow one layer to be visible at once and some will give full layers control to the end user.
Changing Visibility of Layered Content