We had brother machines previously but found that for printing and toner usage per page we were better off with the HP4345 MFP.    The machine itself is expensive but the costs per page was greatly reduced b/c we found an HP compatible extra yield toner and we are very happy.  The Scanning function is terrrifc.  However we have a higher need for faster scanning and use a stand alone Cannon scanner but if we still use our 4345 machines when we are backed up with scanning at the end of the month.     If you sole issue is PDF, then buy the full version of Adobe Acrobat and you can print your .tiff to a PDF and voila, you have a PDF. 

You may want to look at a refurbed machine with a warranty, kinda of like buying a used car with a warranty, there are risks but you have some insurances that you want get stuck.