What Is PDF?

According to Wikipedia, PDF (Portable Document Format) is an open standard for document exchange. This file format created by Adobe Systems in 1993 is used for representing documents in a manner independent of application software, hardware, and operating systems. Each PDF file encapsulates a complete description of a fixed-layout flat document, including the text, fonts, graphics, and other information needed to display it.

A PDF file is often a combination of vector graphics, text, and raster graphics. The basic types of content in a PDF are:

  • text stored as content streams (i.e., not text)
  • vector graphics for illustrations and designs that consist of shapes and lines
  • raster graphics for photographs and other types of image

In later PDF revisions, a PDF document can also support links (inside document or web page), forms, JavaScript (initially available as plugin for Acrobat 3.0), or any other types of embedded contents that can be handled using plug-ins. PDF 1.6 supports interactive 3D documents embedded in the PDF – 3D drawings can be embedded using U3D or PRC and various other data formats.

Two PDF files that look similar on a computer screen may be of very different sizes. For example, a high resolution raster image takes more space than a low resolution one. Typically higher resolution is needed for printing documents than for displaying them on screen. Other things that may increase the size of a file is embedding full fonts, especially for Asiatic scripts, and storing text as graphics.

In order to display / read PDF documents on your computer, you need to install appropriate software called PDF reader / PDF viewer. Some of them (mostly free) are: