"Side by Side is a remarkable free app. With Side by Side, you can split the iPad screen into as many as four windows that can be positioned and sized as needed. These windows can be used to view multiple websites, PDF’s or MS Word files. Or, any of the windows may be used for note-taking text editors. Text can be copied into a text editor from other open windows. Text-to-speech is available in any of the windows via Speak Selection."
Via John Evans