How Can you Cancel your Pre-sale, at the KDP?
Answer: you can't.
When you set up a pre-sale with Amazon, you are given a fixed amount of time in which you may upload the final book. Don't assume that you can upload a final manuscript or file right up to the live pre-sale date; you cannot.
(updated: Amazon is apparently now allowing authors to make one change, to a pre-sale date--to make it earlier. But as we recommend in our Terms & Conditions, please make sure that you have your files in your hands, before you slate your pre-sale. Trust me on this.)
Amazon gives you a "countdown clock," that will show you exactly how much time you have, to upload your final eBook file. If you miss that deadline, the book that gets sent to your buyers will be the last draft manuscript you uploaded.
You can cancel your pre-sale--but if you do that, you lose pre-sale privileges for a year.
Our "Frequently-asked questions about Amazon's publishing program" section is coming soon! Keep your eyes peeled!