All volumes of PSN can be downloaded for free from the PSN website at https://ugp.rug.nl/psn, hosted by the University of Groningen Press.
Printed volumes are not available (anymore).
For general information about the journal, see the PSN website, or https://www.barkhuis.nl/the-petronian-society-newsletter/, or follow the menu to Info | Journals | Petronian Society Newsletter.