Depending on where you are in your program, "preparing a paper" usually refers to one of two things:

While there isn't a single "pbpg.zip" file for the entire program, you can download the essential handbooks and templates directly from the Plant Breeding & Plant Genetics Program site:

It looks like you're working with the program, likely at the University of Wisconsin-Madison, and need to prepare a formal document or research proposal. 1. Downloading Program Resources

Committee documents and specific forms are often hosted in a PBPG Box Folder . 2. Preparing Your Paper

The Plant Genome Author Instructions | Science Societies