I found a better solution from PC Magazine. Their example is for renaming digital camera photo files but I think it could work well for your PDF files as well.
"Used with the /F command line switch, the Windows 2000/XP FOR command parses lines of text into individual words. If the value in parentheses is a filespec, FOR parses each line of each matching file."
"Used with the /F command line switch, the Windows 2000/XP FOR command parses lines of text into individual words. If the value in parentheses is a filespec, FOR parses each line of each matching file."
http://www.pcmag.com/article2/0,4149,1386947,00.asp