iSpring Free - iSpring Free is a free eLearning authoring tool that allows you to create responsive courses and quizzes right in PowerPoint and convert them to HTML5 or SCORM.
Wondershare PDFelement - All-in-one PDF editor
H5P - H5P is a free and open-source content collaboration framework based on JavaScript.
Foxit PhantomPDF - Edit PDF files with our feature-rich PDF Editor. Download Foxit PDF Editor to convert, sign, scan / OCR & more. A speedy PDF Editor alternative to Adobe Acrobat.
Articulate Storyline - Articulate Storyline is a program that allows you to create interactive courses of any kind with templates and a simple system. There is a free trial offered so that you can determine whether you want to use the program further or not.
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.