Start by considering the business of online editing in general.
In traditional editing, you handwrite corrections and comments onto the pages of a printout of the document to be edited. You discuss your recommendations with the writer, discuss why you made some of the recomendations that you did, hear the writer's reasons why some your recommended changes cannot be made, and reach agreements as to which changes the writer will implement. The writer then makes those agreed-upon changes.
In the online version of this process, you as editor actually make proposed changes to an electronic copy of the document. Depending on the software that you and the writer use, the writer can accept or reject your proposed changes.
What's so great about that? When you consider the editing process and the process of incorporating edit comments, you can see that it is duplicated effort. As editor you laboriously hand-mark the changes you believe are needed; the writer then, equally laboriously, enters your proposed changes into the file.
A more efficient process would be for the writer simply to press a button and accept (or reject) each of your proposed changes one by one. For example, if you make a sentence clearer and easier to read, the writer ought to be able to press a button to incorporate that rewrite or reject it if it alters the technical meaning of the sentence.
Most software tools have now added editing and track change tools.
The following links give you an introduction to editing online. Editing online means that you make your editing corrections or markup at the computer, directly into a copy of the writer's file.
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