No, you cannot reconvert to PDF (well, you can, but you'd just create yet another new document, without any annotations whatsoever and with yet more conversion artifacts).
Go to
http://amzn.com/manageyourkindle
Select the Settings tab, and make sure Personal Document Archiving is enabled.
Then your send-to-Kindle documents will be downloadable through Kindle for Android, and will sync between devices.
Kindle for PC does not support PDOCs, but you can manually copy them from your Voyage and add them to My Kindle Content, which should do the same thing.