How can i detect if pdf is opened in program or adobe website extension?

So you want to check if a specific file is opened in the app? What you can do is scan the app.activeDocs array and check the path property of each item in it, and compare it to the path of the file you're interested in. However, this must be done from a privileged context, such as the JS Console.

Oh i might forgot to add that i need to check it via js. These pdfs are available on a websice for customers to fill