Help CenterPlease keep in mind, Low and Medium Content books can not be uploaded as an eBook. People can not write on a eBook, and KDP will reject it.
eBooks are generally for written books, (high content, Novel, Fiction, Non Fiction, Biography, etc) which are made for eReaders. eReaders have no ability to write in answers in a word search, crossword, and other puzzles, etc.
So if you have a written book, that is a Novel, Ifciton, Non Fiction, Biograpphy, etc, and you have a PDF and you want to use the covert your pdf to do eBook. This is pretty easy with the help of a free tool that KDP offers Authors called Kindle Create.
If you made one of these types of written books in Book Bolt (we are not sure why you would since it is not a word processor and Word or Google Docs would do it so much better, then save your project as RGB. Once done that, please see below.
To learn more about it please see these articles from the KDP Help.
Using this tool will allow the end result to be saved in .epub or .kpf format, which is the best format to upload as an ebook.
Create a Cover For eBook: You could do the cover in Book Bolt. Create a new project, pick custom, pick 6 x 9 and one page. Then you create your front cover (no front and back cover in ebook).
Then click file in the Book Bolt Studio and pick export to PNG. You will need to convert that .png file to .jpg, just open it in a graphics program, even Microsoft Paint and click file and save as and pick jpg as the type. Or use good to search png to jpg converter. Upload that jpg as the cover.