Thanks for answering. So you can understand my use case - I have a PDF book I want to sell, and would like to include a customized code in each book. As the book is long, I have no desire to recreate it in your app's Designer.
Off topic, but since PDF files are actually text files for a form of source code, you should be able to put a default code on your document and generate new ones using a search-and-replace script. Sed should do the trick.
No you cannot manipulate existing PDF but only generate new ones. Thanks!