pdfSetLayerVisibility
Set the visibility state of a layer.
void pdfSetLayerVisibility(PDFViewerHandle viewer, PDFLayerHandle layer, int visibility)
This function sets the visibility state of a layer. The visibility
argument should be non-zero to make the layer visible, or zero to make
it not visible.
The layer argument is an opaque layer handle, returned by pdfGetLayer.
C:
PDFLayerHandle layer;
int visible;
layer = getGetLayer(viewer, .....);
visible = pdfGetLayerVisibility(viewer, layer);
/* toggle the layer */
pdfSetLayerVisibility(viewer, layer, !visible);