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What is PDF?

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What is PDF?

Portable Document Format (PDF) is a file format proprietary to Adobe Systems Inc. It is used in 1993 for document exchange first time. It represented two-dimensional documents in a device independent and resolution independent fixed-layout document format. Later, it extended to Acrobat 3D and embedded 3D documents.
PDF is officially declared as an open standard on July 1, 2008. It becomes now ISO 32000 (International Organization for Standardization). According to one estimate, there are more than one billion files are in existence today.
PDF is a digital form of document to view, print, and preserve content and visual appearance, independent of the environment (Microsoft Windows, Apple Macintosh, Unix and Linux and manyy mobile platforms). Its allows users to:
  • preserve document fidelity independent of device or platform
  • merge content from diverse sources
  • edit documents collaboratively in multiple platforms
  • apply digital signatures for authenticity
  • set security and permissions to preserve control over content
  • allow content accessibility for people with disabilities
  • extract and reuse of content in other file formats, and
  • collect and integrate data for business systems
PDF file is set of objects such as numbers and strings. PDF vector images are usually composed of Bézier curves. PDF raster images are represented by dictionaries and streams. Images are compressed using filters:
  • ASCII85: puts the stream into 7-bit ASCII
  • ASCIIHex: same as ASCII85 but less compact
  • Flate: is based on Deflate or Zip algorithm
  • LZW: is based on LZW Compression
  • RLE: is a compression method using Run Length Encoding algorithm
  • DCT: is based on the JPEG standard
  • CCITTFax: is based on CCITT fax compression standard
  • JBIG2: is based on JBIG2 standard, introduced in PDF 1.4
  • JPX: is based on the JPEG2000 standard, introduced in PDF 1.5
Adobe has made many improvements from the PDF version 1.0 released in June 1993.
PDF Version Release Year PDF Reader Features
1.0 1993 Acrobat Reader 1 First release with basic features
1.1 1994 Acrobat Reader 2 Colors, links and passwords
1.2 1996 Acrobat Reader 3 Unicode, multimedia, and mouse events
1.3 2000 Acrobat Reader 4 Digital signatures, ICC color and JavaScript actions
1.4 2001 Acrobat Reader 5 JBIG2, transparency, and OCR text layer
1.5 2003 Adobe Reader 6 JPEG2000, linked multimedia, object streams, and cross reference streams
1.6 2004 Adobe Reader 7 Embedded multimedia and XML forms
1.7 2006 Adobe Reader 8 Digital signatures, ICC color and JavaScript actions
1.7 Extension 2008 Adobe Reader 9 256-bit AES encryption
1.8 2010 Adobe Reader X Commenting, rich multimedia, international standards conformance, software rollouts
Adobe Reader is a free software distributed by Adobe Inc. It can be downloaded by clicking the button:
Get Adobe Reader
There are many other software firms developed PDF readers with different features and file sizes. ISO 32000 protects the PDF integrity and longevity. PDF continues to be used as one of the most trusted file formats.
Go to: What is Word document?
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