How to publish an iBook without using iBooks Author?

Question

I've been reading the various pages on the subject and what I've gathered is:
-If you publish through iBooks Author, you can only sell your book through iBooks.
Is there an option in which you can upload a pdf version of the book?
If so, are you required to provide an ISBN or is there a way around it?

Answer 1

You don't have to use iBooks Author (and books produced by iBA can only be read in the iBooks app on iPads and Macs, they can't be read on iPhones nor iPod Touches), but you can't sell PDFs in the iBookstore - but you can sell epubs in it.
Creating epubs with Pages : Creating ePub files with Pages.
Authors and publishers FAQ : http://www.apple.com/itunes/working-itunes/sell-content/books/book-faq.html
Selling books on iTunes : http://www.apple.com/itunes/working-itunes/sell-content/books/
From the above FAQ :
Do I need an International Standard Book Number (ISBN)?
No, an ISBN is recommended but not required for any book you are offering on the iBooks Store. An ISBN uniquely identifies the book and its current edition, and helps you to ensure that you are marketing the right book. The ISBN is also required for reporting your book's sales to industry reporting agencies and charting organizations.
To obtain an ISBN in the U.S., contact Bowker. To obtain an ISBN outside the U.S., contact the International ISBN Agency.