Layers in the original drawing can be visible (switched on) or hidden (switched
off). To enable processing of layers during the export to PDF, the Enable Layers
Support flag must be switched on. Also, the user can control the export of invisible
layers using the Include Invisible Layers flag.
Enable Layers Support — If off, only visible geometry is exported from the
drawing, and the resulting PDF file has no layers. The Include Invisible
Layers flag value is ignored. If on, layers are exported to the PDF file,
and the list of exported layers depends on the value of the Include Invisible
Layers flag.
Include Invisible Layers — If on, all layers are exported, and the PDF
file contains the same quantity of layers as the original drawing (hidden
layers are also exported). In other words, a fully identical copy of the layers
is created in PDF format. If off, only visible layers are exported, and the
resulting PDF file doesn't contain hidden layers.
Note that exporting layers depends on the rendering mode of the original drawing;
if it is rendered in wireframe mode (with or without the hidden lines removal algorithm),
the output PDF document also contains layers (if Enable Layers Support is switched on of course).
For other rendering modes, layer export is not supported because the content is exported as an image.