A copy of this tutorial in SGML and HTML is distributed with each source code release of GTK+. For binary distributions, please check with your vendor.
A copy is available online for reference at http://www.gtk.org/tutorial.
A packaged verion of this tutorial is available from ftp://ftp.gtk.org/pub/gtk/tutorial which contains the tutorial in various different formats. This package is primary for those people wanting to have the tutorial available for offline reference and for printing.