If you are using our "Upload" writing mode, you can easily upload a new version of your book anytime by going to the "Upload" page for your book here:
...making sure to replace YOUR_BOOK with your book's unique web address.
You can also access this page from the Overview page for your book, in the "Versions" section:
Here is what the Upload page looks like, with a PDF file already uploaded, in this example:
To replace the old file with a new file, just upload the new file, the same way you uploaded the old file.
There's no need to do anything else! Just to be clear, if your book is already published, all of your current and future readers will now get the new file you uploaded, the next time they download the book.