the Compare Documents tool to find "similarities" between two versions of PDF files. I want to check similarities of two different pdf files .Can anyone know about this feature.I repeat to check the similarities not differences

the Compare Documents tool to find "similarities" between two versions of PDF files.I want to check the similarities between two different pdf files ,like same words or sentences that are in two difffrent pdf .I repeat I want to se the similarities not differences.Does anyone know this kind of thing.