2. Note is perfect for this, but a larger tablet like the Galaxy Tab 10.1 might be better if you need them to read text, etc.
3. See 1.
4. Pretty cheap: https://market.android.com/details?i...d.reader&hl=en
Obviously the Note has quite a decent Office suite, but you can buy others if you don't like it, plus Google Docs is free.
Google Navigation is free and works in SA with voice navigation.
Of course this is true of all Android tablets so you can choose anyone and do this stuff. The Note's big advantage is that it fits in your pocket and you can make calls with it. If you plan on doing a lot of work on office document though then a larger tablet (or really a laptop) is a better choice. Tablets and phones will never replace PC's for office work (although the Asus Transformer seems like a great option but it's not strictly a tablet if you use it that way).
Edit: If you need accurate handwriting (for signatures) then your only real options are the Note and the HTC Flyer. Though Samsung are rumoured to be announcing larger tablet Notes soon.
Update: I've just tried out the EZ PDF feature, on an ordinary PDF it will create a separate annotation file for the handwriting, I'm not sure how it will deal with PDF forms as I don't have any. Feel free to PM me a PDF form and I'll try it out for you.