The Samsung Galaxy S4 user's manual is available online for free. To access the manual online go to samsung.com and click "Owners & Support" on the menu bar located on the top of the page, followed by "Manuals & Downloads." Continue by following the instructions provided.
In order to read the manual, you may need to install a PDF reader. The most popular PDF reader is Adobe Acrobat, which is available for free online. To download Adobe Acrobat Reader, go to get.adobe.com/reader/ and then follow the instructions provided. If you need additional help with your Galaxy S4, you can contact Samsung directly.