PDF made from a digitally signed document does not show up the Digital Signature in the PDF Reader

When we export a digitally signed document in libreoffice, and export to pdf, it exports as plain and simple document, the digitally signed property of the document does not pass to the pdf. this means that you need to again sign the pdf document separately. Could the libreoffice team do something about it?

Digital signature is bound to the data file to forbid any tampering with the document. When exporting you get a new data file, and digital signatures can not be transfered.