Autoconf is a GPLv2-licensed package of macros that produces a shell script "configure" to generate a Makefile and config header for a project. The configuration scripts produced by Autoconf are self-contained, so the users of your project do not need Autoconf, M4, or perl to run configure.
By the time you read this, it is possible that the latest version has been updated. You may want to use a newer version, but it's possible a newer version might not work the same way. To ensure a positive outcome, don't upgrade unless you have a good reason to, or if the Autoconf folks recommend you to do so on their website.
As I write this, the latest version of Autoconf is 2.64. You can download this, or another version, at http://ftp.gnu.org/gnu/autoconf/. Assuming you want to install version 2.64: download autoconf-2.64.tar.gz; put this into a temporary folder, such as /tmp/autoconf, and follow the rest of these instructions to install it.
$ mkdir /tmp/autoconf $ cd /tmp/autoconf $ wget http://ftp.gnu.org/gnu/autoconf/autoconf-2.64.tar.gz
$ cd /tmp/autoconf $ gzip -dc < autoconf-2.64.tar.gz | tar -xf - $ cd autoconf-2.64
$ ./configure --prefix=/usr $ make
# make install
This version of Autoconf, when installed, produces the following files: (assuming --prefix=/usr)
I personally dislike outdated documentation. If anything here seems wrong, or perhaps did not work for you, please email me (jay@petio.org) and tell me so I can update it. Thanks!