calibre - Ebook manager, viewer & converter
Google Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.
FBReader - FBReader is an e-book reader for various platforms. Features:
Adobe Acrobat DC - Make your job easier with Adobe Acrobat DC, the trusted PDF creator. Use Acrobat to convert, edit and sign PDF files at your desk or on the go.
Google Play Books - Google Play Books lets you search, preview, and buy millions of books using Google Book Search.
Wondershare PDFelement - All-in-one PDF editor