Part 1: The Carousel Object System

The Portable Document Format (PDF) specification, as released by the International Organization for Standardization (ISO) in the form of a series of related standards (ISO-32000-1 and -2, ISO-19005-1, -2, and -3, ISO-14289-1,...), was originally created by Adobe Systems Inc.

Carousel was the original code name for what later became Acrobat. The name Carousel was already taken by Kodak, so a marketing consultant was asked for an alternative name. These were the names that were proposed:

  • Adobe Traverse– didn't make it,
  • Adobe Express– sounded nice, but there was already that thing called Quark Express,
  • Adobe Gates– was never an option, because there was already somebody with that name at another company,
  • Adobe Rosetta– couldn't be used, because there was an existing company that went by that name.
  • Adobe Acrobat– was a name not many people liked, but it was chosen anyway.

Although Acrobat exists for more than 20 years now, the name Carousel is still used to refer to the way a PDF file is composed, and that's what the first part of this book is about.

In this first part, we'll:

  • Take a look at the basic PDF objects,
  • Find out how these objects are organized inside a file, and
  • Learn how to read a file by navigating from object to object.

After reading this part, you'll know how PDF is structured and you'll understand what you see when opening a PDF in a text editor instead of inside a PDF viewer.