As @Priathic seems to be the one figuring out it was NMS coordinates, could it be that the 5 known pdf so far have in their filenames itself some hidden coordinates?
612040ac-f7d1-4f3d-9969-640bba886a97
75d56807-39b0-42e2-9643-eef45358fb0e
7d3dd080-2a43-4882-833c-f4d7bd7ba607
331c6734-a013-4695-8e47-08a9ee05d5e5
9936c797-ec28-4f8f-b80e-dee9e0b06433
What do you think?
I though these were just names created automatically by the (wordpress?)-site. Hides the real file names and thus prevents anyone from accessing them early by brute-forcing names