From Files view: Tap “Select” in the upper right. Tap a document. Tap “Share.”
From Page view: Tap “Tools” in the upper right.
Options will specify if they only send a copy of the document to the export destination. These options keep the PDFpen edit in PDFpen resulting in two separate documents in separate locations.
If you opened your document from Files view, it will save back to that location. You can email your document, or, export a copy of it into another app, using the Share menu.
Annotations, like comment boxes, highlights, and signatures, can be edited by other PDF editors once you share a document. A way to prevent this is to flatten a document, thereby removing the ability to edit annotations. You can flatten a document upon export from the “Share” menu. This will not effect the version of the document you are currently editing.