PDF export doesn't preserve layer structure

[Cobalt]

When exporting to PDF the layer structure is not the same as in the original document. A lot of top level layers disappear and their contents are spilled.
It seems like if a layer only contains other layers but does not directly contain any geometry then it disappears.
Also groups are not preserved. All their members are spilled to the top directory.

PDF layers.afdesign
PDF layers.pdf

EDIT:
Just in case anyone is wondering, PDF files do support nesting of layers. For example the above PDF manually fixed in some external app:
ManuallyFixed PDF layers.pdf

[Cobalt]

Obviously it is not practical having to go in there every time a PDF is exported and keep manually correcting the layer structure.

[Sean P]

Hi Cobalt,

What external application did you use to modify the layer structure of the PDF? Illustrator will only export top level layers and discard any nested ones.

[WKansepa]

If you want to preserve layer structure try exporting your pdf using the PDF/X-4 setting. 

[Cobalt]

1 hour ago, william said:

If you want to preserve layer structure try exporting your pdf using the PDF/X-4 setting. 

That would be nice, but its not my experience; I tried all PDF presets before posting.

[Cobalt]

On 3/19/2019 at 3:00 AM, Sean P said:

Hi Cobalt,

What external application did you use to modify the layer structure of the PDF? Illustrator will only export top level layers and discard any nested ones.

PDF-XChange PRO
Acrobat PRO can do it too according to their help page
 

Quote

Some layers may be organized into nested groups with a parent layer. Other layers may be in groups with no parent layer.

 

[Loopkin]

On 3/19/2019 at 10:00 AM, Sean P said:

[...]Illustrator will only export top level layers and discard any nested ones.

Hi Sean,

I'm not sure to understand what you said...

Of course Illustrator can export layers and sublayers and groups in pdf... But Designer can't see them...