The file transfer will have to be addressed by others since I don't use a USB cable to transfer files. I am using a method of transferring via SSH which can be a bit complex to set up. Anyways, that is half the battle.

You can download a media converter from the following website that installs on your computer. This should convert the media files you have to a format that the Internet Tablet likes. I'm not quite sure how it handles VOB files though. Essentially, the converter can only convert things that Windows Media Player can understand... so you can understand why I think it might work.
http://www.nokia.com/A4688059

Anyways, it is worth a try.

Unless I am not understanding your problem, the Nokia n800 (at least with the latest OS) can natively understand PDF files. There should be a PDF viewer in Utilities > PDF Reader. You should also be able to just double click on a PDF itself from the File manager (Utilities > File Manager). Is there issues doing that?

There is a dedicated Ebook reader called FBReader but I'm not sure if it likes PDF files... I will have to do some research later. A quick test of me trying to add a PDF file as a book came up with the program not seeing the PDFs so I would think that it doesn't work in that program... not that there was really a need for it to work. FBReader can read other formats (txt, ebook formats, alike) but nothing with DRM in it.