It's scary how such a widely used format (PDF) is almost in full control by Adobe. I have yet to see a true competitor to Adobe Acrobat. The only one that has come really close is the one that comes built-in for macOS. It's a hidden gem.
There's a reason why, unlike raster image formats, there aren't any serious competitors. The thing to realise about printed page file formats is that even if you set aside all of the silly "multimedia" and "interactivity" features, there's still a gargantuan rabbit hole of non-trivial features that need to be implemented absolutely perfectly, from kerning to spot color. PDF does it all very well. There's really no scope for a competitor to come along to make something that's obviously better.