Paper can be between 0.0028 to 0.0071 inches thick depending on its function. As an example, tracing paper is thinner than bond paper because of how it is made, but also because it has to be translucent in order to serve its purpose.
The thickness of paper is affected by its desired use. Pulp is manufactured and manipulated in different ways to obtain the type of paper needed by clients. Printing paper is different in texture and thickness than paper found in note books. Different chemical coatings are also applied to the finished product, depending on what its intended use is.