Most users don’t want to use the CLI.
It seems out of whack to complain about linux without investing a wee bit of time with cli.
but it's not the car's fault if people don't want to use keys to start them up.
anyway, there's a huge amount of GUI software to handle PDFs in Linux, I will say that Linux gives you the most options, either as free software and close source ones.
Hell Acrobat is gold on WineHQ!
But for those who do have the patience and understanding for the shell and man pages, well they can become more powerful than the other Oses combined!