Several different types of snb to pdf conversion exist, but all of them are doable and are about document / publication conversions. The first option represents export ot of Galaxy Notes to PDF format, something that can be only done using the S Note software for desktop.
Another take would be conversion of Shanda Bambooks as PDF documents. For this you would need some ebook management program that still support this type of SNB formatOpen SNB file Open PDF file
A free e-book library management application
Linux version of the popular ebook manager
A free open source ebook creator, converter and viewer
A desktop app for handling S Note documents
A simple converter for S Notes