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Camscanner is really a great application for both android and ios users.
It is used to enhance the captured document in a wonderful way. It crops it nicely and precisely without any lags.
You can also turn it into b/w which is a great feature,it makes every text understandable and clear.
Link for android user: https://play.google.com/store/apps/details?id=com.intsig.camscanner&hl=en_IN
Link for ios user:
https://itunes.apple.com/in/app/camscanner/id388627783?mt=8
Must try this application.