I am exporting a signed PDF to PDF/A with Libreoffice Writer. When I do this, the file is converted to a PDF/A but removes the signature. This happens in the headless aswell as in the GUI.
The PDF was signed with the Portable Signer2
Converting PDF to PDF/A considerably changes the PDF internally, so if the (digital) signature was left in the PDF, it would become invalid in the course of the conversion.