The application/pdf Media Type
draft-hardy-pdf-mime-00

Network Working Group                                           M. Hardy
Internet-Draft                                               L. Masinter
Obsoletes: 3778 (if approved)                                      Adobe
Intended status: Informational                                D. Johnson
Expires: January 22, 2015                                PDF Association
                                                           July 21, 2014

                     The application/pdf Media Type
                        draft-hardy-pdf-mime-00

Abstract

   PDF, the 'Portable Document Format', is an ISO standard (ISO
   32000-1:2008) defining a final-form document representation language
   in use for document exchange, including on the Internet, since 1993.
   This document provides an overview of the PDF format and updates the
   media type registration of 'application/pdf'.  It replaces RFC 3778.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on January 22, 2015.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   include Simplified BSD License text as described in Section 4.e of

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  History . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Fragment Identifiers  . . . . . . . . . . . . . . . . . . . .   3
   4.  Subset Standards  . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Accessibility for PDF . . . . . . . . . . . . . . . . . . . .   5
   6.  PDF Implementations . . . . . . . . . . . . . . . . . . . . .   5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   This document is intended to provide updated information on the
   registration of the MIME Media Type "application/pdf" for documents
   defined in the PDF [ISOPDF], 'Portable Document Format', syntax.
   Additionally, this document provides a brief history of the PDF
   format, describes several of the key capabilities of the format and
   addresses some security concerns.

   PDF is used widely in the Internet community.  The first version of
   PDF, 1.0, was published in 1993 by Adobe Systems [REF needed].  Since
   then PDF has grown to be a widely-used format for capturing and
   exchanging formatted documents electronically across the Web, via
   e-mail and virtually every other document exchange mechanism.  In
   2008, PDF 1.7 was published as an ISO standard [ISOPDF], ISO
   32000-1:2008.

   PDF represents "final form" formatted documents with a fixed layout
   and appearance.  PDF pages may include text, images, graphics and
   multimedia content such as video and audio.  PDF is also capable of
   containing higher level structures including annotations, bookmarks,
   file attachments, hyperlinks, logical structure and metadata.  A rich
   JavaScript model has been defined for interacting with PDF documents.

   PDF supports encryption and digital signatures.  The encryption
   capability is combined with access control information to facilitate
   management of the functionality available to the recipient.  PDF
   supports the inclusion of metadata through XMP [XMP] metadata as well
   as directly via PDF structures.

   In addition to the ISO 32000-1:2008 PDF standard, several ISO PDF
   subset standards have been defined to address specific use cases.

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   These standards include PDF for Archival (PDF/A), PDF for Engineering
   (PDF/E), PDF for Universal Accessibility (PDF/UA), PDF for Variable
   Data and Transactional Printing (PDF/VT) and PDF for Prepress Digital
   Data Exchange (PDF/X).  The subset standards are fully compliant PDF
   files capable of being displayed in a general PDF viewer.

   PDF usage is widespread enough for 'application/pdf' to be used in
   other IETF specifications.  RFC 2346 [RFC2346] describes how to
   better structure PDF files for international exchange of documents
   where different paper sizes are used; HTTP byte range retrieval is
   illustrated using application/pdf (RFC 2616 [RFC2616], Section 19.2);
   RFC 3297 [RFC3297] illustrates how PDF can be sent to a recipient in
   a way that identifies the user's ability to accept the PDF using
   content negotiation.

2.  History

   PDF was originally envisioned as a way to communicate and view
   printed information electronically across a wide variety of machine
   configurations, operating systems, and communication networks in a
   reliable manner.

   PDF relies on the same fundamental imaging model as the PostScript
   [PS] page description language to render complex text, images, and
   graphics in a device and resolution-independent manner, bringing this
   feature to the screen as well as the printer.  However, unlike
   PostScript, PDF enforces page independence, ensuring that any page in
   a document can render without having to render previous pages.
   Additionally, PDF reduces the complexity of processing content to
   improve performance for interactive viewing.  In addition to the
   rendering capabilities, PDF also includes objects, such as hypertext
   links and annotations, that are not part of the page itself, but are
   useful for navigation, building collections of related documents and
   for reviewing and commenting on documents.

   The application/pdf media type was first registered in 1993 by Paul
   Lindner for use by the gopher protocol and was subsequently updated
   in 1994 by Steve Zilles.

3.  Fragment Identifiers

   A set of fragment identifiers [RFC2396] and their handling are
   defined in Adobe Technical Note 5428 [PDFOpen].  This section
   summarizes that material.

   A fragment identifier consists of one or more PDF-open parameters in
   a single URL, separated by the ampersand (&) or pound (#) character.
   Each parameter implies an action to be performed and the value to be

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   used for that action.  Actions are processed and executed from left
   to right as they appear in the character string that makes up the
   fragment identifier.

   The PDF-open parameters allow the specification of a particular page
   or named destination to open.  Named destinations are similar to the
   "anchors" used in HTML or the IDs used in XML.  Once the target is
   specified, the view of the page in which it occurs can be specified,
   either by specifying the position of a viewing rectangle and its
   scale or size coordinates or by specifying a view relative to the
   viewing window in which the chosen page is to be presented.

   The list of PDF-open parameters and the action they imply is:

   namedest=<name>
   Open to a specified named destination (which includes a view).

   page=<pagenum>
   Open the specified (physical) page.

   zoom=<scale>,<left>,<top>
   Set the <scale> and scrolling factors. <left>, and <top> are measured
   from the top left corner of the page, independent of the size of the
   page.  The pair <left> and <top> are optional but both must appear if
   present.

   view=<keyword>,<position>
   Set the view to show some specified portion of the page or its
   bounding box; keywords are defined by Table 8.2 of the PDF Reference,
   version 1.5 (NEEDS UPDATING TO ISO REF).  The <position> value is
   required for some of the keywords and not allowed for others.

   viewrect=<left>,<top>,<wd>,<ht>
   As with the zoom parameter, set the scale and scrolling factors, but
   using an explicit width and height instead of a scale percentage.

   highlight=<lt>,<rt>,<top>,<btm>
   Highlight a rectangle on the chosen page where <lt>, <rt>, <top>, and
   <btm> are the coordinates of the sides of the rectangle measured from
   the top left corner of the page.

   All specified actions are executed in order; later actions will
   override the effects of previous actions; for this reason, page
   actions should appear before zoom actions.  Commands are not case
   sensitive (except for the value of a named destination).

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4.  Subset Standards

   TODO: Describe the subset standards, their history and include
   references to the ISO documents.

5.  Accessibility for PDF

   TODO: Describe the Accessibility capabilities of PDF.

6.  PDF Implementations

   There are a number of widely available, independently implemented,
   interoperable implementations of PDF for a wide variety of platforms
   and systems.  Since the PDF specification was published and freely
   available since the format was introduced in 1993, hundreds of
   companies and organizations, including web-browser developers, make
   PDF creation, viewing, and manipulation tools for many years prior to
   ISO standardization of PDF.

   TODO: Update the above list to ensure relevance to update market
   conditions...

7.  Security Considerations

   TODO: Clean up of this section is still required...

   An "application/pdf" resource contains information to be parsed and
   processed by the recipient's PDF system.  Because PDF is both a
   representation of formatted documents and a container system for the
   resources need to reproduce or view said documents, it is possible
   that a PDF file has embedded resources not described in the PDF
   Reference.

   Although it is not a defined feature of PDF, a PDF processor could
   extract these resources and store them on the recipients system.
   Furthermore, a PDF processor may accept and execute "plug-in" modules
   accessible to the recipient.  These may also access material in the
   PDF file or on the recipients system.  Therefore, care in
   establishing the source, security, and reliability of such plug-ins
   is recommended.  Message-sending software should not make use of
   arbitrary plug-ins without prior agreement on their presence at the
   intended recipients.  Message-receiving and -displaying software
   should make sure that any non-standard plug-ins are secure and do not
   present a security threat.

   PDF may contain "scripts" to customize the displaying and processing
   of PDF files.  These scripts are expressed in a version of
   JavaScript.  They are intended for execution by the PDF processor.

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   User agents executing such scripts or programs must be extremely
   careful to insure that untrusted software is executed in a protected
   environment.

   In general, any information stored outside of the direct control of
   the user -- including referenced application software or plug-ins and
   embedded files, scripts or other material not covered in the PDF
   Reference -- can be a source of insecurity, by either obvious or
   subtle means.  For example, a script can modify the content of a
   document prior to its being displayed.  Thus, the security of any PDF
   document may be dependent on the resources referenced by that
   document.

8.  IANA Considerations

   This document updates the registration of 'application/pdf', a media
   type registration as defined in Multipurpose Internet Mail Extensions
   MIME) Part Four: Registration Procedures [RFC2048]:

   MIME media type name: application

   MIME subtype name: pdf

   Required parameters: none

   Optional parameter: none

   Encoding considerations: PDF files frequently contain binary data,
   and thus must be encoded in non-binary contexts.

   Security considerations: See Section 7 of this document.

   Interoperability considerations: See Section 6 of this document.

   Published specification: ISO 32000-1:2008 (PDF 1.7) [ISOPDF].

   Applications which use this media type: See Section 6 of this
   document.

   Additional information:

   Magic number(s): All PDF files start with the characters '%PDF-'
   using the PDF version number, e.g., '%PDF-1.7'.  These characters are
   in US-ASCII encoding.

   File extension(s): .pdf

   Macintosh File Type Code(s): "PDF "

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   For further information: Duff Johnson <duff.johnson@pdfa.org>, Cherie
   Ekholm <cheriee@microsoft.com>, ISO 32000 Project Leaders

   Intended usage: COMMON

   Author/Change controller: Duff Johnson <duff.johnson@pdfa.org>,
   Cherie Ekholm <cheriee@microsoft.com>, ISO 32000 Project Leaders

9.  References

   [ISOPDF]   ISO, "Document management -- Portable document format --
              Part 1: PDF 1.7", ISO 32000-1:2008, 2008.

              Also available free from Adobe Systems.

   [XMP]      ISO, "Extensible metadata platform (XMP) specification --
              Part 1: Data model, serialization and core properties",
              ISO 16684-1, 2012.

              Not available for free, but there are a number of
              descriptive resources, e.g., [1]

   [PS]       Adobe Systems Incorporated, "PostScript Language
              Reference, third edition", 1999.

              Available at: [2]

   [PDFOpen]  Adobe Systems Incorporated, "PDF Open Parameters",
              Technical Note 5428, May 2003.

              Available at: [3]

   [RFC2048]  Freed, N., Klensin, J., and J. Postel, "Multipurpose
              Internet Mail Extensions (MIME) Part Four: Registration
              Procedures", BCP 13, RFC 2048, November 1996.

   [RFC2346]  Palme, J., "Making Postscript and PDF International", RFC
              2346, May 1998.

   [RFC2396]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifiers (URI): Generic Syntax", RFC 2396,
              August 1998.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

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   [RFC3297]  Klyne, G., Iwazaki, R., and D. Crocker, "Content
              Negotiation for Messaging Services based on Email", RFC
              3297, July 2002.

Authors' Addresses

   Matthew Hardy
   Adobe
   345 Park Ave
   San Jose, CA  95110
   USA

   Email: mahardy@adobe.com

   Larry Masinter
   Adobe
   345 Park Ave
   San Jose, CA  95110
   USA

   Email: masinter@adobe.com
   URI:   http://larry.masinter.net

   Duff Johnson
   PDF Association
   Neue Kantstrasse 14
   Berlin  14057
   Germany

   Email: duff.johnson@pdfa.org
   URI:   http://www.pdfa.org

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