Can the iPad be used to type documents?

The iPad most certainly can be used to type documents.

Originally, one major point of differentiation between the iPad and the smaller iPod touch and iPhone devices is that the iPad exclusively had compatible productivity software -- a version of the iWork Pages, Numbers, and Keynote applications -- for word processing/basic page layout, spreadsheets, and presentations, respectively.

Although Apple subsequently has released versions of these apps for the iPhone and iPod touch, the small displays make the software much less convenient for more than basic review and quick edits of documents, even with the assorted zoom functionality.

Pages, Numbers, and Keynote originally were available for the iPad for free.