The CLP 325 isn't shown as supported on http://support.apple.com/kb/HT3669, and the PPD for the CLP 325 isn't included in what you downloaded. What driver did you use to add the printer?
If you are using the CLP 325W, http://www.samsung.com/us/computer/printers/CLP-325W/XAC-specs shows:
Duplex Printing : Manual
OS Compatibility: Mac OS X 10.3-10.6
Hope this helps.