pdflib-4.0.3 is the latest "free" (Aladdin Free Public License) compilable pdflib version
pecl-pdflib 2.1.10 is the latest version compilable with pdflib < 6!
 source: http://pecl.php.net/package-info.php?package=pdflib&version=2.1.10

pecl-pdflib-2.1.10 was patched by me removing safe_mode in order to get it running with php 5.4.x:
 background info: http://php.net/manual/en/features.safe-mode.php
 --> safe mode:
 This feature has been DEPRECATED as of PHP 5.3.0 and REMOVED as of PHP 5.4.0.