This paper explains about knowledge mining and the relationship between the knowledge mining and the similarity measure. This paper also describes the various document similarity measures, algorithms and to which type of text it can be appliedDocument similarity measures are of full text similarity, paragraph similarity,sentence similarity, semantic similarity, structural similarity and statistical measures.Two different models had been proposed in this paper, one for measuring document to document similarity and the other model which measures similarity between document to multiple document. These two proposed models can use any one of the similarity measures in implementation aspect, which is been put forth for further research.