Documents can be used as archived data which can then be further analyzed and triangulated with other data sources to make claims about a qualitative study.
Some examples of documents are listed below
Picture of a virtual environment in Second Life for my research in Technology-integrated learning and social environments.
Picture of the context in which the participant interacts and details her experiences. This is a picture from my dissertation research where I explored how two female transnational Indian graduate students negotiated their experiences in the formal and informal structures of higher education in the U.S. in their first year of study.
Other examples of documents could be but not limited to:
books websites brochures videos photo albums journals legal documents newspaper articles poems song lyrics letters