An underrated feature of LibreOffice is the ability to insert the original document inside a PDF when exporting. If you reopen that PDF in LibreOffice, it will grab the embedded copy for editing instead of trying to guess how to convert the PDF into its original.
That's monstrous. When I send a PDF I don't want it to be editable, if I wanted an editable format I'd use an editable format. Exporting to PDF is supposed to be a digital equivalent to printing.