The Office Mobile app on Android provides the options to Save or Save As in the menu when viewing and editing documents. Using the Save option will replace the original file with your new edits. The Save As option is similar to using this feature on a computer—it will save a copy of the current file to your Dropbox. Please note that this saves the file in the home (or root) directory of your Dropbox; it will not save to the location of the original file and you won't be able to select a subfolder within your Dropbox to save the file. You can use the Dropbox app, desktop client or website to move the newly edited copy anywhere in your Dropbox, including the original folder location. If the original file is still present, your new file will have a (1) appended to it. Please note that if the original file is stored in a shared folder, and you want the new file to be shared as well, you'll need to to move the newly edited file into the shared folder, or simply use the Save option.