27 Facts About PDF

PDF has its roots in "The Camelot Project" initiated by Adobe co-founder John Warnock in 1991.

The PDF specification provides for encryption and digital signatures, file attachments, and metadata to enable workflows requiring these features.

PDF file is often a combination of vector graphics, text, and bitmap graphics.

PDF is largely based on PostScript but simplified to remove flow control features like these, while graphics commands equivalent to lineto remain.

Linearized PDF files are constructed in a manner that enables them to be read in a Web browser plugin without waiting for the entire file to download, since all objects required for the first page to display are optimally organized at the start of the file.

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Basic design of how graphics are represented in PDF is very similar to that of PostScript, except for the use of transparency, which was added in PDF 1.

Raster images in PDF are represented by dictionaries with an associated stream.

Text in PDF is represented by text elements in page content streams.

Font object in PDF is a description of a digital typeface.

The encoding mechanisms in PDF were designed for Type 1 fonts, and the rules for applying them to TrueType fonts are complex.

Original imaging model of PDF was, like PostScript's, opaque: each object drawn on the page completely replaced anything previously marked in the same location.

The addition of transparency to PDF was done by means of new extensions that were designed to be ignored in products written to PDF 1.

Concept of a transparency group in PDF specification is independent of existing notions of "group" or "layer" in applications such as Adobe Illustrator.

Technically speaking, tagged PDF is a stylized use of the format that builds on the logical structure framework introduced in PDF 1.

The PDF Reference defines ways that third parties can define their own encryption systems for PDF.

Thus, the use restrictions that a document author places on a PDF document are not secure, and cannot be assured once the file is distributed; this warning is displayed when applying such restrictions using Adobe Acrobat software to create or edit PDF files.

One of the significant challenges with PDF accessibility is that PDF documents have three distinct views, which, depending on the document's creation, can be inconsistent with each other.

Rich Media PDF is a PDF file including interactive content that can be embedded or linked within the file.

Some of these vulnerabilities are a result of the PDF standard allowing PDF documents to be scripted with JavaScript.

PDF viewers are generally provided free of charge, and many versions are available from a variety of sources.

RIPs capable of processing PDF directly include the Adobe PDF Print Engine from Adobe Systems and Jaws and the Harlequin RIP from Global Graphics.

PDF released an upgrade to their Harlequin RIP with the same capability in 1997.

The submission of press-ready PDF files is a replacement for the problematic need for receiving collected native working files.

In 2006, PDF was widely accepted as the standard print job format at the Open Source Development Labs Printing Summit.

Some desktop printers support direct PDF printing, which can interpret PDF data without external help.

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PDF was selected as the "native" metafile format for Mac OS X, replacing the PICT format of the earlier classic Mac OS.

System-level support for PDF allows Mac OS X applications to create PDF documents automatically, provided they support the OS-standard printing architecture.