What is .PDF File Extension?

A Brief Details about what is PDF File Format!

PDF (portable document format) is a cross-platform two-dimensional document file created by Acrobat program, Acrobat Capture, or similar products of Adobe Systems. A .pdf document file keeps all the elements such as: text, fonts, images, and 2D vector graphics, etc. The PDF file has also taken all the features of a printed document as an electronic image, navigate, forward to somebody or, print.

PDF files are used for personal as well as a business both purposes because it contains one or more page images, Hyperlinks, different font styles, Quicktime, AVI movies and buttons for forms entry or triggering sound, etc. The Adobe reader is a free program provided by Adobe System which stops query how to open .pdf files. Apart from Adobe reader, a few more free PDF reader are available that can be used to read portable document format. Hope now you will understand what is pdf file format, for more details continue reading…

PDF File Format Basic Structure!

Above section specifies what does pdf mean and now the basic structure of an Adobe PDF document file is shown in below image:

1. Header: First line of a PDF file that specifies the version number of the used PDF specification which the document uses is called the header.
   # xxd temp.pdf | head -n 1
   0000000: 2550 4446 2d31 2e33 0a25 c4e5 f2e5 eba7 %PDF-1.3.%......
   
2. Body: The Body section of PDF file is used to contain the entire document's data being shown to the user.
3. xref Table: This is the cross reference table, which encloses the references to all the objects in the document.
   

   xref
   0 1
   0000000023 65535 f
   3 1
   0000025324 00000 n
   21 4
   0000025518 00002 n
   0000025632 00000 n
   0000000024 00001 f
   0000000000 00001 f
   36 1
   0000026900 00000 n

4. Trailer: The PDF trailer identifies how the app analyzing the PDF document would find the cross reference table & other special objects.
   

   trailer
   <<
   /Size 22                    - where /Size [integer]            
   /Root 2 0 R            - where /Root [dictionary]
   /Info 1 0 R
   >>
   startxref
   24212
   %%EOF

Note: These were file structure details of the extension.pdf. To view PDF file format structure you can open your PDF file with a hex editor or edit plus programs.

Programs to Open or Read PDF File Extension

PDF file is a portable document format can be read with a lot of free tool across all the platforms.

Software to Open PDF in Windows OS:

1. Adobe Reader
2. Adobe Acrobat
3. Google Chrome
4. Mozilla Firefox
5. Foxit Reader
6. PDF Architect
7. Soda PDF
8. Free PDf to DOC Converter
9. Web browser with Adobe Reader plug-in

Programs to Open PDF File in MAC OS X:

1. Adobe Acrobat for Mac
2. Apple Preview
3. Adobe Reader
4. Google Chrome
5. Mozilla Firefox

Read PDF File in Linux:

1. Google Chrome
2. Mozilla Firefox
3. LibreOffice
4. KDE Okular

Access PDF File in IOS:

1. Adobe Debut
2. Apple iBooks
3. GoodReader

Open PDF File in Android:

1. Adobe Reader
2. Quickoffice Pro

View PDF File in Windows Phone:

1. Adobe Systems