You'll need to be more specific about your workflow.
I assume you are talking about the equivalent of target="_blank" in an HTML anchor tag, but in what scenario? Do you mean you want a link embedded in a PDF file to open in a new window? This is the default behavior in Acrobat, it will open links in the system-specified application based on the link type (i.e. 'mailto' will open in your default mail client, 'http' will open in your web browser).