I recently installed payflow. I located libpfpro.so on my system and then set the LD_LIBRARY_PATH to include it. That path ended up with the directory containing libpfpro.so, /lib, and /usr/lib. I also had to set the PFPRO_CERT_PATH environment variable to the directory where the cert lives (hint the .so file is in a directory which is a sybling of the directory where the cert lives.)

Phil