The most convenient way how to export notes from Galaxy S Note files (.spd) would be to download the S Note for Windows desktop from Samsung website, import the note there and export it as a .pdf document. This pretty much what spd to pdf conversion represents, i.e. export of the notes to PDF format.
Something similar can be probably achieve via syncing the note with Evernote and printing it as PDF from the desktop version of that program, but that seems to be unnecessary unless you are using Evernote already.