There have been occasional forum posts asking about the availability of previous IDPA rule books.
Thanks to Dru Nichols, Ted Murphy, Lance Biddle, Steve Koski, and others, several old versions have been gathered.
December 17, 2014 -
December, 2014 clarification (final consolidated clarification for 2013 rule book)
October 1, 2013 -
2013 rulebook (The "Flat-Footed Reload Rule Book")
July 6, 2010 -
2010 rule addendum (update to 2005 rule book)
April 15, 2005 -
The Little Brown Book (April, 2005 to October, 2013)
May 2, 2001 -
The Little Green Book (May, 2001 to April, 2005)
March 1, 2000 -
The Little Red Book (March, 2000 to May, 2001)
The Little Red Book - *scanned* (not searchable)
October 27, 1998 -
October, 1998 *scanned* rule book (not searchable)
November 7, 1997 -
November, 1997 *scanned* rule book (not searchable)
July 7, 1997 "Update" rule book -
July 7, 1997 OCR rule book (searchable)
October, 1996 - two versions -
October, 1996 *scanned* rule book (not searchable)
October 26, 1996 OCR rule book (searchable, but with some weird character recognition)