Question about Mac Voiceover accessibility

I've been thinking about possibly making the switch to a Mac at some point in the future and, although I've been researching hese questions, I still don't have a clear answer, so I'm hoping my knowledgeable friends can give me more definite answers.

Does Voiceover work with the following programs and formats:
Firefox
ePUB
PDF
Flash

Also, are there any Voiceover users out there who do a lot of scanning and OCR use and, if so, what program and hardware are you using? I'm really not keen on the Docuscan approach of having to send everything I scan to the Internet.