$ wget -r --no-parent -A '*.pdf' http://hackerschool.org/HardwareHacking/

   -A acclist --accept acclist

   -R rejlist --reject rejlist

       Specify comma-separated lists of file name suffixes or patterns to 

       accept or reject. Note that if any of the wildcard characters, *, ?,

       [ or ], appear in an element of acclist or rejlist, it will be 

       treated as a pattern, rather than a suffix.

   --accept-regex urlregex

   --reject-regex urlregex

       Specify a regular expression to accept or reject the complete URL.

Posted by Forensist