As an alternative, there is libbfd (backend for GCC and others): Documentation and download
I took a quick look at the PeLib review, but it doesn't seem worse in availability. I don’t know what you expect from such a library, but most object format libraries have no idea what you expect from them, and therefore do not have much access. In other words: such a library only saves you from parsing the format of an object.
If you want to do something specific, it will help us learn about it.