Ebook or simple PDF to choose on a landing page?


I would like to create a landing page with a downloadable file on it. Could you pls tell me...

1.) Should I create a formal ebook or a simple PDF is enough? (the text is 3 pages only)
2.) Whats the best format (software) for ebooks and for PDF creation?
3.) Is it better if its really downloadable or just readable (on Amazon S3 for excample)
4.) If its better to read only, how to protect the file (on Amazon S3 or by a plg)