Usually, to read a Microsoft word file, PDF documents or watch PowerPoint presentation find on the internet, firstly you need to download the file and open it in an appropriate application. But with the Documents Preview Opera extension, you can read them without downloading.
After installation, Documents Preview extension prompts for document preview when you click links pointing to the files such as .DOC .PPT or .PDF files. It uses Google documents viewer for this.
Documents Preview requires Opera 11 and the extension can be downloaded at Opera extension gallery