PEP is an acronym for PDF Editing Program for Mac. It's free and open source. It's designed to be a fast , robust and lightweight alternative to Adobe Acrobat. The development is in its early stage, and all releases by now are alpha release, and releases are sent out frequently.
Currently, as the author of PEP, I am the only developer for PEP, I put a lot time into the development every day and night. I write code, test, design and plan the whole develpment. I make all things from scratch , especially the core of this project - Gene (A PDF engine). So PEP does not rely on third-party PDF libraries.
If you are interested in the code, just check it out on Github.
If you would like to support me, please donate on my Patreon.
I am Aaron Elkins, contact me here for anything about PDF, PEP.