Somewhat dated now, but still useful. A general account of data compression algorithms, aimed clearly at programmers – all the main algorithms are implemented in C in the text. The emphasis is on practicalities – this book will not satisfy mathematicians. Among the algorithms included are Huffman, Lempel–Ziv in all varieties, and JPEG.
PDF is now an ISO standard, and the actual standard is only available from ISO, who charge for it. However, Adobe have produced a document that is identical in content, which you can get for free from this page. They also intend to produce supplements describing changes as new versions of the format are introduced. The PDF reference was published in book form in 1993 by Addison-Wesley as “Portable Document Format Reference Manual”, but the format is extended with each release of Acrobat, so it is probably better to refer to the Web version.