Although PDF is primarily used as a read-only format, there are tools for editing PDFs – and indeed, many people pay quite a bit of money for these tools, such as Adobe Acrobat Pro.
But there are alternatives! LibreOffice Draw provides a powerful PDF editor, for free, and since LibreOffice 6.4 it has a great feature

Our old Extensions and Templates Website has worked well over the years. It is one of the key and most frequented websites of the LibreOffice project, as it enables users to enhance the functionality of LibreOffice with add-ons and plug-ins, while providing an easy way for authors to improve LibreOffice.
We’d

Berlin, February 27, 2020 – The Document Foundation announces LibreOffice 6.4.1, the 1st minor release of the LibreOffice 6.4 family, targeted at technology enthusiasts and power users. LibreOffice 6.4.1 includes 80 bug
Berlin, February 20, 2020 – The Document Foundation announces LibreOffice 6.3.5, the 5th minor release of the LibreOffice 6.3 family, targeted at individuals using the software for production purposes, who are invited to
LibreOffice is the successor project to OpenOffice, which had its last major release (4.1) back in 2014, as you can see in this timeline – click to enlarge. And, of course, it’s still free and open source:

We release a new major version every six months – so let’s check out

FOSDEM is the biggest European get-together of free and open source software (aka FOSS). And, of course, the LibreOffice community and certified developers were there!
Indeed, many developers and community members gave talks about their recent work – check out these links for the videos and slides…
Main track