A PDF that’s only on your hard drive is a lonely thing: it wants to go out into the world and meet people, it was born to go out into the world. If you love your PDFs, let them go.
You can make your PDFs public (because that’s what “publish” means in the broadest sense) in many ways:
You can email them.
You can post them on the Web.
You can print them on your printer.
You can send them to a professional print service.
You can send them to your publisher as camera-ready copy.
Notice that, with the exception of printing them on your printer, all of these start with saving your PDF in one way or another.
So let’s start there, too.
When you create or modify a PDF with PDFpen, sooner or later you are going to save ...