In the past, I used to refer to ISO-32000 whenever somebody asked me questions such as "why can't I use PDF as a format for editing documents" or whenever somebody wanted to use a feature that wasn't supported out-of-the-box.
I soon realized that answering "read the specs" is lethal when the specs consist of more than a thousand pages. In this iText tutorial, I'd like to present an introduction to the syntax of the Portable Document Format. It's not the definitive guide, but it should be sufficient to help you out when facing a PDF-related problem.
You'll find some simple iText 7 examples in this book, but the heavy lifting will be done in the other iText books.