I tried to use the the php4.3.2 rpms with pdflib 4.0.3 but it doesn't work. The same library works with php 4.3.2 compiled from source. You can find the library at http://www.pdflib.com/pdflib/download/PHP-4.3.0/pdflib-4.0.3-Linux-php430.tar.gz
The error message when i install the library is PHP Warning: Unknown(): Unable to load dynamic library '/usr/lib/php/extensions/libpdf_php.so' - /usr/lib/php/extensions/libpdf_php.so: undefined symbol: php_file_le_fopen in Unknown on line 0