Using PHP 4.3.0 and PDFLIB 4.0.3 with the PHP 4.3.0 patch (pdf.c) I can't compile PHP.  I build PDFLIB from source, copied the pdf.c and config.php-406+.m4 to the php-4.3.0/ext/pdf directory (the config to config.m4).

Configured PHP with:
./configure --prefix=/opt/php --exec-prefix=/opt/php --with-mysql --with-apache=../apache_1.3.27 --with-pdflib

Since PDFLIB base directory is /usr/local I didn't specify a PDFLIB path.

It configures fine, but during the make I get (last few lines of output):

ext/mysql/libmysql/my_tempnam.o: In function `my_tempnam':
/root/source/php-4.3.0/ext/mysql/libmysql/my_tempnam.c:103: the use of `tempnam' is dangerous, better use `mkstemp'
main/internal_functions_cli.o: In function `php_startup_internal_extensions':
/root/source/php-4.3.0/main/internal_functions_cli.c:69: undefined reference to `pdf_module_entry'
collect2: ld returned 1 exit status
make: *** [sapi/cli/php] Error 1

If you need more output, let me know.  I have never successfully built PHP with PDFLIB on all sorts of different platforms.  I'm surprised other people have been able to.