Yes.

Start BookSmart, open your book, make the changes, then upload (Order Button) to the Blurb server again. It will not overwrite your existing book but create a second copy. You will ned to buy that within 15 days otherwise it will be deleted.

I tend to delete the existing book from the Blurb server before I upload the new one, that way I can’t get muddled about which is which.

…..Tony