Instead of open u can use xdg-open which does the same thing, independently of application i.e. pdf, image, etc. It will open a new virtual terminal (I have tried this on Linux)
Example:
xdg-open ~/Pictures/Wallpapers/myPic.jpg
xdg-open ~/Docs/holidays.pdf
For linux, use xdg-open. open is for Mac OS. open in linux is an name alias of openvt (open virtual terminal).
To simplify it, you can append the following line to ~/.bashrc or ~/.zshrc depends on the shell you are using.
alias o=”xdg-open” # o stands for open
Then next time you can just type like the following to reduce some keyboard strokes.
o file_name.pdf