The Collaborative International Dictionary of English v.0.48:

Stationer \Sta"tion*er\ (-[~e]r), n. [Cf. Stationary, a.]
   1. A bookseller or publisher; -- formerly so called from his
      occupying a stand, or station, in the market place or
      elsewhere. [Obs.] --Dryden.
      [1913 Webster]

   2. One who sells paper, pens, quills, inkstands, pencils,
      blank books, and other articles used in writing.
      [1913 Webster]

WordNet (r) 3.0 (2006):

stationer
    n 1: a merchant who sells writing materials and office supplies
         [syn: stationer, stationery seller]