You could use DVD Access feature in DVDSP but with the newer OSs, it will not work properly – especially on PCs. Its a dinosaur feature that is more or less inoperable.
Best and only option is to create a menu with direction to the PDFs next to the VIDEO_TS folder. You add these with the DVD ROM feature in DVDSP. There are tones of tutorials and the Mnual has info on it as well