In case you missed his original post, he specifically mentioned the need to download PDF files posted from his teacher. Where you got video streaming out of that, I don't know.
OP said "PDA," and I didn't know quite what that was, but "PDF" certainly makes sense as an interpretation. My point is that there's a lot of content out there that can be downloaded from the internet using apps built for the purpose.
Ditto for web-based content, including .pdfs. I have an iPhone, not an iPad, but I can download .pdfs very easily. For example, I just used it to navigate to TraderJoes.com, clicked on Stores, clicked on Find A Store, and clicked on their Northern California link. Voila, a .pdf listing of the region's stores opened up in new window. Went back and clicked on their Southern California link. It opened a second .pdf in a different window. It also has no trouble opening .pdfs emailed to me.
I guess I'm still a little mystified what the OP wants to do.