From my experience, not very much, at least for editing PDFs without fucking up the fonts

Unfortunately in LibreOffice all the pages in a PDF need to render with the same orientation and size :/ It adds whitespace to pages to make them all the same size, and this whitespace remains even when exporting as PDF.

There's been a formal request made to change that, but it's been years with no movement.

Proprietary :-/ but might still be interesting nevertheless

Thanks for sharing