I have a class that makes use of the php_printer extension but I can't find it anywhere and at php.net it says it's currently unavailable. I googled it, but all I downloaded from other sites was not efficient. It seemed to me it was outdated. I copied the .dll file in the extensions folder and set the configuration in php.ini but I still couldn't use its built-in functions.I have PHP 5.3.1 installed.
Then you did not google very well. There still are repositories of precompiled binaries elsewhere:
Just saying it does not work is insufficient. I understand that compiling from source is effortful on Windows (pecl install printer given a proper compiler setup), but at the very least run the PHP interpreter on the commandline after editing the php.ini. It would give you a useful error message in case of linking errors, or none in case you edited the wrong config file. (Too few details to answer.)
See also: PHP 5.4.7 Compiling ext php_printer