Keeping two or more pdf documents open and separate using Preview

One difficulty with Preview, which I repeatedly run into, is viewing two or more separate pdf documents at the same time. Preview app seems to require that all open pdfs be displayed serially in Preview. Navigating between the documents requires shifting between thumbnails displayed in the sidebar. This makes it awkward to compare the documents and do other tasks that could be handled more easily if the documents were displayed side by side. Is there a way to open two or more Preview windows, in order to put each pdf document in its own Preview window? Then the documents could be viewed side by side.