its not as effective as StirlingPDF, people using iLovePDF usually need it because they have to edit a PDF with customized footer/upper part of the page and just opening with LibreOffice Writer definitely will not maintain that. keeping the content and format are two different things, so if you are just opening a simple PDF without much formatting then yes maybe you dont need something like StirlingPDF and just directly opening with LibreOffice Writer will suffice