I installed it by copying the PHP_PDF.DLLl in the extensions folder and modified the php.ini file. When I run the sample script from PHP5 documentation I get the following error:
The specified CGI application misbehaved by not returning a complete set of HTTP headers. The headers it did return are:
PDFlib exception (fatal):  PDF_set_parameter: Unknown key 'objorient'
Error in my_thread_global_end(): 1 threads didn't exit