If you want to open something using a specific application (ie opening PDFs with only Acrobat Reader) these are the steps you will need to follow.
Open Windows menu and search for "Default Apps".
Once you are in that window, scroll down to the bottom. You will have two options.
First option is "Choose default apps by file type". If you know the file type, in our example it would be .pdf, you can go with this option. Once you click that link, it will take you to a page that looks like this.
You will find the file type on the left hand side and change the default app associated with it on the right side.
If you click this link, you will choose which file types are opened by what application. Instead of finding the file type, you will search for the application you are looking for.
Once you click on the application, it will show you every file type that can be opened using that application.
You can change the default application by clicking the application on the right.