Know any offline pdf converting app

I would like to know offline pdf converting app. i used ‘PDF converter’ and ‘PDF Creator’ is was great but suddenly editing and sorting doesn’t work and would like to know a better pdf compresser offline.

And for PDF viewer I use Librera Pro which is the best I have seen. Anyone knows better once.

I think PDF converter was the best and there aren’t many alternatives.

Librera is a fully featured viewer, specially for books, but I feel it bloated and sometimes slow.
If you just want to view PDF maybe MuPDF will do the work too, is lightweight.

Well,thanks .
But my main problem is Pdf converter and compresser.