The current trend toward high-performance mobile networks and increasingly sophisticated mobile devices has fostered the growth of mobile workers. In mobile environments, an urgent need exists for handling documents using a mobile phone, especially for browsing documents and viewing Rich Contents created on computers. This paper describes Seamless Document Handling, which is a technology for viewing electronic documents and Rich Contents on the small screen of a mobile phone. To enhance operability and readability, we devised a method of scrolling documents efficiently by applying document image processing technology, and designed a novel user interface with a pan-and-zoom technique. We conducted on-site observations to test usability of the prototype, and gained insights difficult to acquire in a lab that led to improved functions in the prototype.