Hard to say… are the PDF files being served up by a web server? (e.g. fpmi.net.openURL(“http://zeta/manual.pdf”) )
Or were you using windows filesharing on your internal network (e.g. fpmi.net.openURL("\\zeta\manual.pdf") )
The latter won’t from outside your network unless you open up the windows filesharing port, which would be unadvisable…