The Save As command is a useful tool on any computer, but it is mysteriously buried on OS X. It goes missing from the default File menu on Apple's own apps and requires an awkward, four-button keyboard shortcut (Option+Shift+Command+S).
There are two ways you can return the Save As command to its rightful place in the File menu. The first is a quick but temporary shortcut, and the second is a permanent fix for added it back to the File menu.
1. Option key to the temporary rescue
If you are using an Apple app such as Pages, Preview and TextEdit, open the File menu and hold down the Option key. You will notice that Save As takes the place of Duplicate, letting you save a new version of your file without automatically duplicating it by adding "copy" to its title.
2. System Preferences for a permanent fix
To add Save As back to the File menu for Apple apps, open System Preferences and click on Keyboard. Next, click on the Shortcuts tab and choose App Shortcuts from the left panel. Click the "+" button to create a new shortcut.
In the Menu Title field, type "Save As..." -- adding the ellipses if you want the command to appear in its most authentic form.
In the Keyboard Shortcut field, add the keyboard shortcut of your choice, such as Command-Shift-S.
Finally, click the Add button and the next time you are using an Apple app, you'll see the Save As... command between Save and Duplicate.
(Via Apple World Today and OS X Daily)