If I open the same file twice in Okular, switch to the existing window

I have always been confused why the file manager in Linux cannot stop applications from opening a single file twice at the same time? Specifically, I want to stop the PDF file reader Okular from opening the file A.pdf again when I have already opened it. I need to get an warning or just show me the opened copy of the file A.pdf. More generally, I would like this to happen with any application, not just Okular. I want to make the document management behavior in Linux the same as in Windows.