Working with an existing PDF doc

Hi gang: I can create a pdf document "on-the-fly" pretty easily, as shown here: http://xn--ovg.com/pdf However, what I need is to find out how to open an existing pdf document and insert data into it -- does anyone have any experience in doing this, or references they can point me to? As always, mondo thanks for those who reply. tedd -- ------- http://sperling.com http://ancientstones.com http://earthstones.com