subject: Basics Of A Pdf File Structure [print this page] Portable Document Format is a binary or two-dimensional file format that is non-editable. This is a computer application that enables a user to archive and exchange data as well as create electronic documents. A Portable Document Format supports various fonts, images, text search hyperlinks, bookmarks as well as two-dimensional vector graphics. It also supports interactive page elements, annotations, compression, encryption, JavaScript actions and much more. Due to the advanced security features, a user can keep the confidential information secure and intact. This format makes the task of a user more flexible.
History of PDF:
Adobe Systems introduced the first version of PDF in 1993. The computer application underwent many revisions to introduce to the world most modified version. Later versions of PDF supported multimedia elements, advanced color features, digital signatures, image masking and smooth shading, sophisticated web-capture features and advanced trapping capabilities.
File Structure of PDF:
A Portable Document Format is composed of four main parts. These are one-line header, body, cross-reference table and trailer.
Header of the PDF:
The first line of the Portable Document Format specifies the version of a PDF file format. These headers are the topmost portion of a document. A user can also customize the text and the fonts of a header.
Body of PDF:
The body of a PDF file consists of objects that compose the contents of the document. These objects include image data, fonts, annotations, text streams and much more. A user can also integrate invisible objects or elements. These objects embed the interactive features in a document like animation or graphics. A user can also implement logical structure in the document. One can also make the content of a document more secure by implementing security features. A user can protect the content of a document from unauthorized printing, viewing, editing or modifying. The body of a PDF also supports two types of numbers called integers and real numbers.
Cross-Reference Table:
The cross-reference table consists of links to all the objects or elements in a file. A user can deploy this feature to navigate to other pages or content in a document. When a person updates a PDF file, it automatically gets updated in the cross-reference table. One can also trace the updated changes in the cross-reference table.
Trailer:
The trailer enables a user to navigate to the next page by clicking on the link provided.
