27 Facts About PDF


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

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

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

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

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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.

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

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

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

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

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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.

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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.

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

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

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

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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.

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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.

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

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

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

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

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

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

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

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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.

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

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