There's a way to author a DVD that also contains additional files, such as a folder of PDF

If you want the user to be able to put the DVD in a player and watch the videos or put it in their computer like a data DVD to get downloadable files like PDFs or JPEGs then this is what you have to do:

In DVD Studio Pro choose Window/Outline View (command-5) and select the DVD or go to the Graphical View (command-4) and click in a grey area to select the DVD.

With the DVD selected click on the General tab of the Inspector. At the bottom of the window is a section called DVD-ROM. Click the Content checkbox and use "Choose..." to navigate to a folder you'd like to include.

Also note that if you just choose a folder, then only the contents of the folder will get placed at the root level of your disc. If you view it in your Finder when it is burned you'll get the VIDOEO_TS folder, AUDIO_TS folder and all the files that were in the DVD-ROM folder...

If you want to keep things neat and tidy, put all the files in a folder (call it something like 'Files') and then put that folder into another folder (call it something like 'DVD-ROM-Content'). Now in DVD Studio Pro point at the 'DVD-ROM-Content' folder. When the disc is burned you'll get the 'Files' folder on the root of the disc, which will result in better presentation and organization of files on your DVD.