The Collaborative International Dictionary of English v.0.48:

Pledgeor \Pledge*or"\, Pledgor \Pledg*or"\, n. (Law)
   One who pledges, or delivers anything in pledge; a pledger;
   -- opposed to pledgee.
   [1913 Webster]

   Note: This word analogically requires the e after g, but the
         spelling pledgor is perhaps commoner.
         [1913 Webster]