I have a curve 8310 on O2, so I think that this should be relevent to your Bold or Curve 8900.
I think that the 4.6 OS will come pre-installed (if not you can download it) with the "standard" version of Documents to go (
PDA Software - BlackBerry Software, iPhone Software, iPod touch Software, Palm OS Software, webOS Software, Google Android Software, Windows Mobile Software, Windows Smartphone Software, Symbian S60 Software - Developed By DataViz) which enables you to VIEW ONLY .pdf .doc .xls and .ppt files.
If you wish to create new documents and or edit them on the Blackberry you will have to upgrade to the premium version of documents to go, which costs around £60, I think.
HTH