The Portable Document Format (PDF) is the world’s leading page description language, and the first format equally useful for print and online use. PDF documents are now almost ubiquitous in the printing industry, in document interchange, and in the online distribution of paginated content. They are, however, widely viewed as opaque and delicate and are poorly understood, even by those of a technical disposition. This is partly due to a perplexing lack of documentation; the file format reference is freely available, but is of a size and complexity which requires a time investment unlikely to be plausible for the majority of those working with PDF. This book aims to be an approachable introduction. It is suitable both for the technically-minded, and for those who just want to understand a little of the PDF format to give context to their work with tools which produce or process PDF documents.