Taking screen shot is a great way to capture information and make it portable. Usual way of saving a webpage by pressing CTRL + S, create a folder and an html file that need to place together in order to work. Another way is to make PDF file of the page. Both of these techniques disturb the original layout and styling of the page. To keep everything as it appears to you and a format that does not require any special software like a PDF Reader you need to make a image of the content.
Simple Print Screen Button will only capture the visible screen region. In order to capture full screen in Google Chrome Browser you need to install an extension from the Chrome Web Store. You install the extension Full Page Screen Capture in your chrome web browser by simply clicking on the link. The extension is opensource and full source code is available on GitHub.
Once it is fully installed a small camera Icon will be available next to address bar. Below is the gif that explain the process.