When a document is printed and this document contains plural sorts of data such as a document, a presentation material, and a drawing, a virtual document is formed by which these plural data can be printed in a batch mode in a document processing apparatus. Initially, key engine parameters are measured. A guide portion guides the developer to the developer carrier and forms a buffer portion that temporarily contains the developer fed from the developing chamber between the regulating member and the guide portion. The filtering assembly also includes a compliable member that has a thickness that is radially variable downhole.