Check out the copy on DataViz's product page:

Documents To Go is the only product on the market today with support for native Word, Excel, PowerPoint, PDF and TXT files as well as native JPEG and BMP graphics. You can even use files saved to expansion cards or sent as e-mail attachments directly on your smartphone or PDA without synchronization. Most importantly, your original desktop documents will never lose formatting when you make edits on your device using DataViz's unique InTact Technology.

Of course, such functionality does come at a price; the most basic version of DTG for the Palm OS goes for $30. The $50 Premium version provides the promised support for Office 2007 documents. Thanks to Gadgets on the Go for the heads-up.