If you absolutely must edit your own document, take steps to avoid pitfalls and produce acceptable work.
It’s that new gaze, unfamiliar with the material, that will find issues and help you put the final polish on
The mechanics of writing are like the frame of your house. Make them solid and secure, and then get creative.
If you can write the case study so a potential customer feels like you’ve just pulled up a chair and chatted about a story, it will be very effective.
Using words incorrectly can make a reader think we really don’t know what we’re talking about, even if we’re trying to convey valuable information.
A case study is much more likely to be a genuine “customer testimonial.”