If you own a Brother MFC-8670DN printer, and have a typical 64-bit Windows 8 or a Windows 8.1 laptop (or desktop), you may have discovered that the built-in Windows 8 drivers only support the most basic of printing capability. You can't even duplex print. Ugh.
If you searched for print drivers, you probably ended up over at Brother's website, and discovered that they do not have Windows 8 print drivers either, and they say use the built-in drivers. Ugh.
There is hope, though: Use Windows 7 drivers instead. Go to the Brother site for the MFC8670-DN and choose Windows® 7 (64-bit). The driver download is about 40mb size, so it took a couple of minutes. You have to run the download as Administrator, so after the file is downloaded to your PC, locate the file MFC-8670DN-inst-win7-A2, right click it, and pick "Run as Administator". You will eventually get prompted to run the Setup.exe file, and of course, you do so. When all is said and done, you'll have the full printer driver package installed with all the bells and whistles. Duplex printing, manual feed, all that. Enjoy.