Network Working Group M. Hardy
Internet-Draft L. Masinter
Obsoletes: 3778 (if approved) D. Markovic
Intended status: Informational Adobe
Expires: October 9, 2016 D. Johnson
PDF Association
M. Bailey
Global Graphics
April 7, 2016
The application/pdf Media Type
draft-hardy-pdf-mime-01
Abstract
<1>
The Portable Document Format (PDF) 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".
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 9, 2016.
Copyright Notice
Copyright (c) 2016 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
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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 . . . . . . . . . . . . . . . . . . . . . . 7
5. PDF Implementations . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
Appendix A. Changes since RFC 3778 . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
<2>
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.
<3>
PDF was originally envisioned as a way to reliably communicate and
view printed information electronically across a wide variety of
machine configurations, operating systems, and communication
networks.
<4>
PDF is used to represent "final form" formatted documents. PDF pages
may include text, images, graphics and multimedia content such as
video and audio. PDF is also capable of containing auxiliary
structures including annotations, bookmarks, file attachments,
hyperlinks, logical structure and metadata. These features are
useful for navigation, building collections of related documents and
for reviewing and commenting on documents. A rich JavaScript model
has been defined for interacting with PDF documents.
<5>
PDF used the imaging model of the PostScript [PS] page description
language to render complex text, images, and graphics in a device and
resolution-independent manner.
<6>
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 document and object-level metadata through
the eXtensible Metadata Platform[XMP].
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2. History
<7>
PDF is used widely in the Internet community. The first version of
PDF, 1.0, was published in 1993 by Adobe Systems. 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.
<8>
The ISO TC-171 committee is presently working on a refresh of PDF,
known as ISO 32000-2, with a version of PDF 2.0, expected to be
published in 2017.
<9>
In addition to ISO 32000-1:2008 and 32000-2, several subset standards
have been defined to address specific use cases and standardized by
the ISO. 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.
3. Fragment Identifiers
<10>
A set of fragment identifiers [RFC3986] and their handling are
defined in ISO 32000-2 [ISOPDF2]. This section summarizes that
material.
<11>
A fragment identifier is comprised of one or more parameters
separated by the AMPERSAND (&) character. Each parameter implies an
action to be performed on the document and provides values to be used
for that action; the values for a parameter are introduced by an
EQUAL SIGN (=) and separated by a COMMA (,); values which are strings
appear in the fragment identifier using URI's percent-hex escaping --
spaces, reserved and non-ASCII strings are included by %nn encoding
the UTF-8 of each character. Actions shall be processed and executed
from left to right as they appear in the character string that makes
up the fragment identifier.
<12>
The parameters listed in this section operate on the document at the
point it is opened; for this reason they are sometimes referred to as
PDF open parameters. The fragment identifier should be processed
immediately after document-specified open parameters have been
processed.
<13>
The table below lists the PDF open parameters relevant to PDF. All
coordinate values (left, right, top, and bottom) shall be expressed
in the default user space coordinate system.
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<14>
PDF Open Parameters
+-------------+-------------------------+---------------------------+
| Parameter | Arguments | Description |
| Name | | |
+-------------+-------------------------+---------------------------+
| "nameddest" | _name_ | Open the document to the |
| | | specified named |
| | | destination. The |
| | | argument provided is a |
| | | string which shall |
| | | correspond to the name of |
| | | a destination in the |
| | | target document. |
| "page" | _pageNum_ | Open the document to the |
| | | specified page number. |
| | | The argument shall be a |
| | | positive integer number. |
| | | The first page in the |
| | | document has a pageNum |
| | | value of 1. |
| "zoom" | _scale scale,left,top_ | Open the document with |
| | | the specified zoom level |
| | | and optional offset. The |
| | | scale argument shall be |
| | | either an integer or |
| | | floating point value |
| | | representing the |
| | | percentage to which the |
| | | document should be |
| | | zoomed, where a value of |
| | | 100 would correspond to a |
| | | zoom of 100%. The left |
| | | and top arguments are |
| | | optional, but shall both |
| | | be specified if either is |
| | | included. The left and |
| | | top arguments shall be |
| | | integer or floating point |
| | | values representing the |
| | | offset from the left and |
| | | top of the page in a |
| | | coordinate system where |
| | | 0,0 represents the top |
| | | left corner of the page. |
| "view" | _keyword,position_ | Open the document with |
| | | the specified destination |
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| | | set as the view. The |
| | | arguments shall |
| | | correspond to those found |
| | | in [ISOPDF2] 12.3.2.2, |
| | | "Explicit destinations". |
| | | The keyword shall |
| | | correspond to one of the |
| | | keywords defined in |
| | | [ISOPDF2] Table 149, |
| | | "Destination syntax" with |
| | | appropriate position |
| | | values. |
| "viewrect" | _left,top,width,height_ | Open the document with |
| | | the specified window view |
| | | rectangle. The left and |
| | | top arguments shall be |
| | | integer or floating point |
| | | values representing the |
| | | offset from the left and |
| | | top of the page in a |
| | | coordinate system where |
| | | 0,0 represents the top |
| | | left corner of the page. |
| | | The width and height |
| | | arguments shall be |
| | | integer or floating point |
| | | values representing the |
| | | width and height of the |
| | | view. |
| "highlight" | _left,right,top,bottom_ | Open the document with |
| | | the specified rectangle |
| | | highlighted. Each |
| | | argument shall be an |
| | | integer or floating point |
| | | value representing the |
| | | rectangle measured from |
| | | the top left corner of |
| | | the page. |
| "comment" | _commentID_ | Open the document with |
| | | the specified comment |
| | | selected. The commentID |
| | | shall be the value of an |
| | | annotation name, which is |
| | | defined by the NM key in |
| | | the corresponding |
| | | annotation dictionary |
| | | (see 12.5.2 "Annotation |
| | | dictionaries", Table |
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| | | 167). If the comment |
| | | parameter is combined |
| | | with another parameter |
| | | that defines a specific |
| | | page to be displayed, |
| | | then the comment |
| | | parameter shall appear |
| | | after that in the URI. |
| | | Note: The NM key is |
| | | unique to a specific |
| | | page, but is not |
| | | guaranteed to be unique |
| | | to a document. Unless |
| | | the page on which the |
| | | comment resides has been |
| | | selected prior to the |
| | | comment parameter, the |
| | | comment will not be |
| | | selected. |
| "search" | _wordList_ | Open the document and |
| | | search for one or more |
| | | words, selecting the |
| | | first matching word in |
| | | the document. The |
| | | wordList argument defines |
| | | the search words and |
| | | shall be a string |
| | | enclosed within quotation |
| | | marks comprised of |
| | | individual words |
| | | separated by space |
| | | characters. Note that |
| | | the space characters must |
| | | be encoded. |
| "fdf" | _URI_ | Open the document and |
| | | then import the data from |
| | | the specified FDF or XFDF |
| | | file. The URI shall be |
| | | either a relative or |
| | | absolute URI to an FDF or |
| | | XFDF file. The fdf |
| | | parameter should be |
| | | specified as the last |
| | | parameter to a given URI. |
| | | Note: The fdf parameter |
| | | is recommended to be the |
| | | last parameter so that |
| | | the document can open |
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| | | directly to the |
| | | appropriate view. |
+-------------+-------------------------+---------------------------+
4. Subset Standards
<15>
Several subsets of PDF have been published as distinct ISO standards:
<16>
o PDF/X, initially released in 2001 as PDF/X-1a [ISOPDFX], specifies
how to use PDF for graphics exchange, with the aim to fascilitate
correct and predictable printing by print service providers. The
standard has gone through multiple revisions over the years and
has several published parts, the most recently released being part
8, specifying different levels of conformance: PDF/X-1a:2001, PDF/
X-3:2002, PDF/X-1a:2003, PDF/X-3:2003, PDF/X-4, PDF/X-4p, PDF/X-5,
PDF/X-5g, PDF/X-5pg and PDF/X-5n.
<17>
o PDF/A, initially released in 2005, specifies how to use PDF for
long-term preservation (archiving) of electronic documents. It
prohibits PDF features which are not well suited to long term
archiving of documents. Its requirements for PDF/A viewers
include color management guidelines and support for embedded
fonts. There are three parts of this standard and a total of
eight conformance levels: PDF/A-1a, PDF/A-1b, PDF/A-2a, PDF/A-2b,
PDF/A-2u, PDF/A-3a, PDF/A-3b and PDF/A-3u.
<18>
o PDF/E, initially released in 2008 as PDF/E-1 [ISOPDFE], specifies
how to use PDF in engineering workflows, such as manufacturing,
construction and geospatial analysis. Future revisions of PDF/E
are supposed to include support for 3D PDF workflows.
<19>
o PDF/VT, initially released in 2010, specifies how to use PDF in
variable and transactional printing. It is based on PDF/X, and
adds adidtional restrictions on PDF content elements and
supporting metadata. It specifies three conformance levels: PDF/
VT-1, PDF/VT-2 and PDF/VT-2s [ISOPDFVT].
<20>
o PDF/UA, initially released in 2012 as PDF/UA-1 [ISOPDFUA],
specifies how to create accessible electonic documents. It
requires use of ISO 32000's Tagged PDF feature, and adds many
requirements regarding semantic correctness in applying logical
structures to content in PDF documents.
<21>
All of these subset standards use "application/pdf" media type. The
subset standards are generally not exclusive, so it is possible to
construct a PDF file which conforms to, for example, both PDF/A-2b
and PDF/X-4 subset standards.
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<22>
PDF documents claiming conformance to one or more of the subset
standards use XMP metadata to identify levels of conformance. PDF
processors should examine document metadata streams for such subset
standards identifiers and, if apropriate, label documents as such
when presenting them to the user.
5. PDF Implementations
<23>
PDF format has gone through several revisions, primarily for the
addition of features. PDF features have generally been added in a
way that older viewers 'fail gracefully' because they can just ignore
features they do not recognize, but even so, the older the PDF
version produced, the more legacy viewers will support that version,
but the fewer features will be enabled.
<24>
PDF files are experienced through a reader or viewer of PDF files.
For most of the common platforms in use (iOS, OS X, Windows, Android,
ChromeOS, Kindle) and for most browsers (Edge, Safari, Chrome,
Firefox), PDF viewing is built-in. In addition, there are many PDF
viewers available for download and install. The PDF specification
was published and freely available since the format was introduced in
1993, so hundreds of companies and organizations make tools for PDF
creation, viewing, and manipulation.
6. Security Considerations
<25>
The PDF file format allows several constructs which may compromise
security if handled inadequately by PDF processors. For example:
<26>
o PDF may contain scripts to customize the displaying and processing
of PDF files. These scripts are expressed in a version of
JavaScript and are intended for execution by the PDF processor.
<27>
o PDF file may refer to other PDF files for portions of content
using XObjects. PDF processors are expected to find these
external files and load them in order to display the document.
<28>
o PDF may act as a container for various files embedded in it (for
example, as attached files). PDF processors may offer
functionality to open and display such files or store them on the
system.
<29>
o PDF files may contain links to content on the internet. PDF
processors may offer functionality to show such content upon
following the link.
<30>
In addition, the PDF processor itself, as well as its plugins,
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scripts etc. may be a source of insecurity, by either obvious or
subtle means.
7. IANA Considerations
<31>
This document updates the registration of "application/pdf", a media
type registration as defined in [RFC6838]:
<32>
Type name: application
<33>
Subtype name: pdf
<34>
Required parameters: none
<35>
Optional parameter: none
<36>
Encoding considerations: binary
<37>
Security considerations: See Section 6 of this document.
<38>
Interoperability considerations: See Section 5 of this document.
<39>
Published specification: ISO 32000-1:2008 (PDF 1.7) [ISOPDF]. ISO
32000-2 (PDF 2.0) [ISOPDF2] is currently under development.
<40>
Applications which use this media type: See Section 5 of this
document.
<41>
Fragment identifier considerations: See Section 3 of this document.
<42>
Additional information:
<43>
Deprecated alias names for this type: none
<44>
Magic number(s): All PDF files start with the characters '%PDF-'
followed by the PDF version number, e.g., "%PDF-1.7". These
characters are in US-ASCII encoding.
<45>
File extension(s): .pdf
<46>
Macintosh file type code(s): "PDF "
<47>
Person & email address to contact for further information: Duff
Johnson <duff@duff-johnson.com>, Peter Wyatt
<Peter.wyatt@cisra.canon.com.au>, ISO 32000 Project Leaders
<48>
Intended usage: COMMON
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<49>
Restrictions on usage: none
<50>
Author/Change controller: ISO 32000 is by ISO/TC 171/SC 02/WG 08,
"PDF specification". Duff Johnson <duff@duff-johnson.com> and Peter
Wyatt <Peter.wyatt@cisra.canon.com.au are current ISO 32000 Project
Leaders.
8. References
[ISOPDF] ISO, "Document management -- Portable document format --
Part 1: PDF 1.7", ISO 32000-1:2008, 2008.
Also available free from Adobe Systems.
[ISOPDF2] ISO, "Document management -- Portable document format --
Part 2: PDF 2.0", ISO 32000-2.
Currently under development - publication expected in
2017.
[ISOPDFX] ISO, "Graphic technology -- Prepress digital data exchange
using PDF -- Part 8: Partial exchange of printing data
using PDF 1.6 (PDF/X-5)", ISO 15930-8:2008, 2008.
[ISOPDFA] ISO, "Document management -- Electronic document file
format for long-term preservation -- Part 3: Use of ISO
32000-1 with support for embedded files (PDF/A-3)",
ISO 19005-3:2012, 2012.
[ISOPDFE] ISO, "Document management -- Engineering document format
using PDF -- Part 1: Use of PDF 1.6 (PDF/E-1)",
ISO 24517-1:2008, 2008.
[ISOPDFVT]
ISO, "Graphic technology -- Variable data exchange -- Part
2: Using PDF/X-4 and PDF/X-5 (PDF/VT-1 and PDF/VT-2)",
ISO 16612-2:2010, 2010.
[ISOPDFUA]
ISO, "Document management applications -- Electronic
document file format enhancement for accessibility -- Part
1: Use of ISO 32000-1 (PDF/UA-1)", ISO 14289-1:2014, 2014.
[XMP] ISO, "Extensible metadata platform (XMP) specification --
Part 1: Data model, serialization and core properties",
ISO 16684-1, 2012.
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Not available for free, but there are a number of
descriptive resources, e.g.,
<http://en.wikipedia.org/wiki/
Extensible_Metadata_Platform>
[PS] Adobe Systems Incorporated, "PostScript Language
Reference, third edition", 1999.
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013,
<http://www.rfc-editor.org/info/rfc6838>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<http://www.rfc-editor.org/info/rfc3986>.
<51>
This specification replaces RFC 3778, which previously defined the
"application/pdf" Media Type. Differences include:
<52>
To reflect the transition from a proprietary specification by Adobe
to an open ISO Standard, the Change Controller has changed from Adobe
to ISO, and references updated.
<53>
The overview of PDF capabilitiies, the history of PDF, and the
descriptions of PDF subsets were updated to reflect more recent
relevant history.
<54>
The section on Fragment identifiers was updated to closely reflect
the material which has been added to ISO-32000-2.
<55>
The status of popular PDF impelementations was updatd.
<56>
The Security Considerations were updated to match current status.
<57>
The registration template was updated to match RFC 6838.
Authors' Addresses
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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
Dejan Markovic
Adobe
345 Park Ave
San Jose, CA 95110
USA
Email: dmarkovi@adobe.com
Duff Johnson
PDF Association
Neue Kantstrasse 14
Berlin 14057
Germany
Email: duff.johnson@pdfa.org
Martin Bailey
Global Graphics
2030 Cambourne Business Park
Cambridge CB23 6DW
UK
Email: martin.bailey@globalgraphics.com
URI: http://www.globalgraphics.com
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