Yes, I realize other Dell support pages state that none of their printers work with Macs.  However, Dell does provide an official Mac driver for the 1815dn.  Go figure?  Everything prints fine except for PDFs created from my Fujitsu ScanSnap.  The PDF prints as a negative image.  For example, a document with a white background and black text will print from Preview (or Acrobat Pro) with a black background and white text.  However, if the scanned PDF has a little bit of color...it will print just fine.

Anybody have any ideas?

I first thought it was the ScanScap, but the PDF prints fine from WinXP.  However, PDFs not created using the ScanSnap print fine from the Mac.  Is there some kind of wacky printing properties stored in the PDF file that are only honored by a Mac?