[poppler] multilayer PDF

[Valerio Messina]

hi,
I'm trying to join two MULTI-layer PDF files each composed of 1 page:

$ pdfunite pdfFile_pag1.pdf pdfFile_pag2.pdf pdfFile.pdf

The result is a two page PDF MONO-layer.
Seems the multilayer are flettened.
poppler 0.41 on Ubuntu 16.04
Is this know/want?

Joining the PDF with Acrobat, then using 'pdfseparate', preserve the 
layers on all pages. So seems in some manner the library manage layers.

Looking at:
https://poppler.freedesktop.org/releases.html
and:
https://cgit.freedesktop.org/poppler/poppler/tree/TODO
I cannot find mention of "layer".
Will 0.55 pdfunite work well with multilayers PDF ?

Valerio