How to reduce amount of language proofreading of my revised paper? I'm a non-native author and I have a revised paper that has been edited for good English before the first review. Now I made major changes, but still a large part of my essay remained as before. What is the best way to get my revised paper edited for English and flow without having to get charged for the whole (relatively long) paper again? Was someone in a similar situation?
I am a native English speaker, this is based off my experiences proofreading papers for others in my lab who are not native speakers.

Changing even a small section of a paper can have repercussions throughout the rest of the paper in unexpected ways. Also, as important as it is that the English in the changed sections is correct it is also important that those changed sections flow appropriately with the rest of the paper. 

To help with both of these issues it is best to have the entire paper proofread again. Even as a native-English speaker, I have others proofread my paper after revisions because of the above issues. It can be helpful to somehow mark the changed sections and request that the proofreader be aware that those areas were changed.