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  1. PDF - Wikipedia

    en.wikipedia.org/wiki/PDF
    • History
    • Technical Foundations
    • File Format
    • Imaging Model
    • Additional Features
    • Licensing
    • Security
    • Software
    • Alternatives
    • See Also

    Adobe Systems made the PDF specification available free of charge in 1993. In the early years PDF was popular mainly in desktop publishing workflows, and competed with a variety of formats such as DjVu, Envoy, Common Ground Digital Paper, Farallon Replica and even Adobe's own PostScriptformat. PDF was a proprietary format controlled by Adobe until it was released as an open standard on July 1, 2008, and published by the International Organization for Standardization as ISO 32000-1:2008, at which time control of the specification passed to an ISO Committee of volunteer industry experts. In 2008, Adobe published a Public Patent License to ISO 32000-1 granting royalty-freerights for all patents owned by Adobe that are necessary to make, use, sell, and distribute PDF-compliant implementations. PDF 1.7, the sixth edition of the PDF specification that became ISO 32000-1, includes some proprietary technologies defined only by Adobe, such as Adobe XML Forms Architecture (XFA) and JavaScript...

    A PDF file is often a combination of vector graphics, text, and bitmap graphics. The basic types of content in a PDF are: 1. Text stored as content streams (i.e., not encoded in plain text); 2. Vector graphics for illustrations and designs that consist of shapes and lines; 3. Raster graphics for photographs and other types of images 4. Multimedia objects in the document. In later PDF revisions, a PDF document can also support links (inside document or web page), forms, JavaScript (initially available as a plugin for Acrobat 3.0), or any other types of embedded contents that can be handled using plug-ins. PDF combines three technologies: 1. A subset of the PostScriptpage description programming language, for generating the layout and graphics. 2. A font-embedding/replacement system to allow fonts to travel with the documents. 3. A structured storage system to bundle these elements and any associated content into a single file, with data compressionwhere appropriate. PostScript is a p...

    A PDF file contains 7-bit ASCII characters, except for certain elements that may have binary content.The file starts with a header containing a magic number (as a readable string) and the version of the format, for example %PDF-1.7. The format is a subset of a COS ("Carousel" Object Structure) format. A COS tree file consists primarily of objects, of which there are nine types: 1. Boolean values, representing true or false 2. Real numbers 3. Integers 4. Strings, enclosed within parentheses ((...)). Strings may contain 8-bit characters. 5. Names, starting with a forward slash (/) 6. Arrays, ordered collections of objects enclosed within square brackets ([...]) 7. Dictionaries, collections of objects indexed by names enclosed within double angle brackets (<<...>>) 8. Streams, usually containing large amounts of optionally compressed binary data, preceded by a dictionary and enclosed between the stream and endstreamkeywords. 9. The nullobject Furthermore, there may be comments, introdu...

    The 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 1.4. PDF graphics use a device-independent Cartesian coordinate system to describe the surface of a page. A PDF page description can use a matrix to scale, rotate, or skew graphical elements. A key concept in PDF is that of the graphics state, which is a collection of graphical parameters that may be changed, saved, and restored by a page description. PDF has (as of version 2.0) 25 graphics state properties, of which some of the most important are: 1. The current transformation matrix(CTM), which determines the coordinate system 2. The clipping path 3. The color space 4. The alpha constant, which is a key component of transparency 5. Black point compensationcontrol (introduced in PDF 2.0)

    Logical structure and accessibility

    A "tagged" PDF (see clause 14.8 in ISO 32000) includes document structure and semantics information to enable reliable text extraction and accessibility. Technically speaking, tagged PDF is a stylized use of the format that builds on the logical structure framework introduced in PDF 1.3. Tagged PDF defines a set of standard structure types and attributes that allow page content (text, graphics, and images) to be extracted and reused for other purposes. Tagged PDF is not required in situations...

    Optional Content Groups

    With the introduction of PDF version, 1.5 (2003) came the concept of Layers. Layers, or as they are more formally known Optional Content Groups (OCGs), refer to sections of content in a PDF document that can be selectively viewed or hidden by document authors or consumers. This capability is useful in CAD drawings, layered artwork, maps, multi-language documents, etc. Basically, it consists of an Optional Content Properties Dictionary added to the document root. This dictionary contains an ar...

    Encryption and signatures

    A PDF file may be encrypted, for security, in which case a password is needed to view or edit the contents. PDF 2.0 defines 256-bit AES encryption as standard for PDF 2.0 files. The PDF Reference also defines ways that third parties can define their own encryption systems for PDF. PDF files may be digitally signed, to provide secure authentication; complete details on implementing digital signatures in PDF is provided in ISO 32000-2. PDF files may also contain embedded DRMrestrictions that pr...

    Anyone may create applications that can read and write PDF files without having to pay royalties to Adobe Systems; Adobe holds patents to PDF, but licenses them for royalty-freeuse in developing software complying with its PDF specification.

    In November 2019, researchers from Ruhr University Bochum and Hackmanit GmbH published attacks on digitally signed PDFs .They showed how to change the visible content in a signed PDF without invalidating the signature in 21 of 22 desktop PDF viewers and 6 of 8 online validation services by abusing implementation flaws.On the same conference, they additionally showed how to exfiltrate the plaintext of encrypted content in PDFs.In 2021, they showed new so-called shadow attacks on PDFs that abuse the flexibilty of features provided in the specification.An overview of security issues in PDFs regarding denial of service, information disclosure, data manipulation, and Arbitrary code executionattacks was presented by Jens Müller. PDF attachments carrying viruses were first discovered in 2001. The virus, named OUTLOOK.PDFWorm or Peachy, uses Microsoft Outlookto send itself as an attached Adobe PDF file. It was activated with Adobe Acrobat, but not with Acrobat Reader. From time to time, new...

    Viewers and editors

    PDF viewers are generally provided free of charge, and many versions are available from a variety of sources. There are many software options for creating PDFs, including the PDF printing capabilities built into macOS, iOS, and most Linux distributions, LibreOffice, Microsoft Office 2007 (if updated to SP2) and later, WordPerfect 9, Scribus, numerous PDF print drivers for Microsoft Windows, the pdfTeX typesetting system, the DocBook PDF tools, applications developed around Ghostscript and Ado...

    Printing

    Raster image processors (RIPs) are used to convert PDF files into a raster format suitable for imaging onto paper and other media in printers, digital production presses and prepress in a process known as rasterisation. RIPs capable of processing PDF directly include the Adobe PDF Print Engine from Adobe Systems and Jaws and the Harlequin RIP from Global Graphics. In 1993 the Jaws raster image processor from Global Graphicsbecame the first shipping prepress RIP that interpreted PDF natively w...

    Native display model

    PDF was selected as the "native" metafile format for Mac OS X, replacing the PICT format of the earlier classic Mac OS. The imaging model of the Quartz graphics layer is based on the model common to Display PostScript and PDF, leading to the nickname Display PDF. The Preview application can display PDF files, as can version 2.0 and later of the Safari web browser. System-level support for PDF allows Mac OS X applications to create PDF documents automatically, provided they support the OS-stan...

    The Open XML Paper Specification is a competing format used both as a page description language and as the native print spooler format for Microsoft Windows since Windows Vista.

    • 15 June 1993; 27 years ago
    • ISO 32000-2
    • 2.0
    • Adobe Inc. (1993–2008), ISO (2008–)
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