Manage Your E-books with Calibre (Kindle Fire)

Kindle Fire HD 7", Dolby Audio, Dual-Band Wi-Fi, 16 GB - Includes Special Offers

Calibre is a free and open source e-book library management application developed by users of e-books for users of e-books. Especially if you have a tablet with small memory, you better convert it your better use. In my case, it's really good to convert almost PDF ebooks to .MOBI, AZW3 or EPUB (NOOK, Aldiko) format. Because, I can't manage well all of my ebooks well in DOCS, so you should make them appear in BOOKS location. 

Step 1. Download and install suitable version of Calibre to your machine

Step 2. Add your ebooks to Calibre and start to convert