How can I edit a PDF document on OS X?
FormulatePro is an excellent free and open source app for OS X that lets you annotate, edit, insert graphics, fill out forms, and otherwise manipulate PDF documents.
For an example, here is a PDF that comes from OS X.
I’ll open it with FormulatePro to just type in some notes. FormulatePro uses the native PDF printing of OS X to then save a new PDF.
I inserted a random image, and some text:
And here is my final random annotated example: [PDF]