Can an editor make substantial edits to an author's book or paper and publish them without the author's permission?
Editorial review is an iterative process in which an editor, reviews and the author(s) have open (although usually blind) exchanges about the details of a manuscript. The process relies wholly on a full exchange of information between all parties.
A helpful and detailed account of a standard editorial process may be found at the National Institutes for Health website.
As Cape Code remarks in a comment, things are probably different for books and papers.
For what concerns papers, it would be probably very difficult, if not impossible, for an editor to make substantial edits without author's approval for the following reasons:
- The editor might not have access to the paper source files, which are frequently managed by another office.
- The author usually has to approve the galley proofs before publication, and the editor changes would be easily detected. And if the editor makes a number of unapproved last minute changes, the author would be able to use the approved galley proof to put up a case against the editor.
If you have to ask the question, then it is not your original work. As you said, you are "editing". Editors are not the original writers.
When you change the structure of the sentence, you are paraphrasing the original passage and therefore, the original author gets credit for that!
In lieu of direct permission, a citation is an absolute must before you publish.