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Save As disappeared in OS X Lion, but it has returned in Mountain Lion as a hidden option in "File" menu and as a shortcut. To use it in Lion, see > http://reviews.cnet.com/8301-13727_7-57447094-263/restore-save-as-functionality- in-lion-with-hot-key-shortcuts/
Command-Shift-S invokes 'Save as' in all apps that support it as of 10.8.
I'd suggest upgrading for the sake of $20 (assuming your machine is supported) since much in Lion that was bad is not so bad in Mountain Lion.
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