What are PDF File Type Extensions?

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The Portable Document Format (PDF)

Portable Document Format (PDF) is a file format created by Adobe Systems Inc., and supported in Adobe Acrobat, Adobe reader, and many other third-party PDF reading and processing software.

The PDF is a text based document format, which grew up to include any type of multimedia. The primary aim of PDF is to render files like articles, e-books, etc., as a printable document. Other document formats like HTML may not be quite friendly with printers. Therefore, their outputs usually go askew when printed. The PDF documents are created by digital printing (usually from documents in another format). It is not an easily editable format.

The format can “port” a document from one platform to another, and that’s how it got its name. This means that the format can support multiple platforms or Platform Independence. Platform independence enables the document to be viewed independent of the viewer, OS, and the file system.

PDF is an open standard file format. PDF, which is based on Adobe’s previous format, PostScript (PS), is now a standard for the printable document formats.

Adobe Acrobat is the ultimate PDF printing and editing software. Adobe reader, a free application supplied by Adobe, is the viewer for PDF files. Still, Acrobat cannot edit PDF files like how we edit a word document. PDF is almost a final document, and it cannot be edited fully (only addition or minor editing of lines of text can be done). So, it is advisable that you edit any document to its final form before you print it as a PDF document. Also, preserve the base document in case an editing is required in the future. In such case, the PDF document will have to be reprinted from the edited original document.

PDF’s other capabilities include fully searchable index (in text based documents), digital signature in documents, password protection, Text To Speech (TTS), etc.

PDF is now an ISO 32000 standard, and has these subsets: PDF/A (for archiving), PDF/X (for Graphics), and PDF/E (for Engineering Exchange).

PDF is perhaps the most popular internet format for the downloadable documents. People send files, which are either e-books or any other such printable material, to their customers using this format. Its platform independence strengthens its popularity.

The Format Description of PDF

The PDF format consists mainly of objects, which are of eight main types: Boolean values, numbers, strings, arrays and other ordered lists, dictionaries (indexed collection of objects), streams, and the null object.

MIME type (Multipurpose Internet Mail Extension): It is used to identify the document when sent cross-platform, attached in an email.

application/pdf
application/x-pdf
application/acrobat
applications/vnd.pdf
text/pdf
text/x-pdf

Identifying Characters: The characters appearing at the start of the PDF document that uniquely identify the file type.

Hex: 25 50 44 46 2D 31 2E
ASCII: %PDF-1

Adobe PDF’s most important characteristic is that it looks as exactly as it would when printed, for it can preserve the fonts, graphics description, and any other attribute of the document. PDF’s subsets, PDF/X, PDF/A, and PDF/E are also recognized by the ISO standards committee, and are being developed as open standards as well. Adobe family alone doesn’t support the PDF. Being an open standard, PDF Software Development Kit (PDF SDK) can be downloaded free of charge directly from Adobe’s website. The companies download the PDF SDK, and use it without needing to pay any royalty to them. However, Adobe retains the patent to PDF.