Linking vs. Attaching PDF Files

As part of an extranet application, I need to display pdf files. As some of the information is sensitive, I want to make sure that access to these documents is secure. The traditional Domino approach is to attach each of the files to a Notes document with appropriate reader security.

We have another web application (ASP) that also displays links to pdf’s – in this case stored on a file server. The intersesting thing is that when I try to access another pdf (by changing the URL to a different file name), I get an error. In essense, I cannot display any PDF file other than one that has a link on the page!

The other developer says that they are not doing anything to implement security on these filse. Can anyone explain this behavior? I have always considered files stored on the file system to be unsecure unless some type of file protection is implemented.

Thanks!