Sustainability of Digital Formats
Planning for Library of Congress Collections
Sustainability of Digital Formats
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | PDF/X |
| Description | PDF/X is a subset of the Adobe Portable Document Format (PDF) specification that is intended to reflect best practices in graphic arts file exchange. The aim is for a digital content file that will run through prepress without requiring rework or causing errors and be printed predictably and correctly whether it is a single print job or a magazine ad placed in many publications and printed across the world. For simplicity, the description here currently focuses on the 2003 versions of the PDF/X standard, based on Adobe PDF version 1.4. For most purposes, the discussion applies also to the first versions of the PDF/X standard, based on PDF 1.3. There are plans to bring out updates in 2006 based on PDF version 1.6. PDF/X restricts the content in a PDF document, prohibiting elements that do not directly serve the purpose of high-quality print production output, such as annotations, Java Actions, and embedded multimedia. PDF/X also eliminates the most common errors in file preparation. Profiles 1a and 3 are intended to support "blind" exchange of graphics files with all elements within a single file. Profile 2 is less constrained but assumes that the two parties share information through other means. Constraints for blind exchange include: • All fonts and images must be embedded • Boxes that specify the print and trim areas must be explicitly defined. • Trapping status must be explicit. [Trapping controls overlap of elements in different layers and applied through separate printing processes; a small degree of overlap is desirable to allow for imprecise registration in the printing process. Trapping can be applied before or after exchange; but should not be applied more than once.] • Colorspaces must be specified in a device-independent manner • Encryption is disallowed in all PDF/X files compliant with 2003 versions of the standard. |
| Production phase | A middle-state format for exchange during prepress activities. Serves as a final-state digital format to the extent that it is used for online proofing prior to printing. |
| Relationship to other formats | |
| Subtype of | PDF (Portable Document Format) |
| Subtype of | PDF_1_4 |
| Has subtype | PDF/X-1a_2003, not yet described. |
| Has subtype | PDF/X-3_2003, not yet described. |
| Has subtype | PDF/X-2_2003, not yet described. |
| LC experience or existing holdings | None. |
| LC preference | LC is likely to prefer PDF/A over PDF/X when either could be used. Among the PDF/X profiles, LC will prefer those intended for blind exchange. |
| Disclosure | Open standard. Prepared by Technical Committee ISO/TC 130, Graphic technology, in collaboration with the United States national body Committee for Graphic Arts Technologies Standards (CGATS) with administrative support from NPES. NPES is a trade association of over 400 companies which manufacture and distribute equipment, systems, software, supplies used in printing, publishing and converting. The standard is maintained by CGATS Subcommittee 6 Task Force 1. |
| Documentation | ISO 15929. Graphic technology - Prepress digital data exchange - Guidelines and principles for the development of PDF/X standards. Specific PDF/X profiles (including the subtypes noted above) are documented in separate parts of ISO 15930. |
| Adoption | Many magazines and journals require that all advertising materials be submitted as PDF/X or TIFF/IT files. As of Spring 2005, it appears that PDF/X is typically preferred over TIFF/IT. According to February 2005 minutes of the Subcommittee maintaining the standard, most use is technically based on the PDF/X versions published in 2001. Acrobat 7 from Adobe will create PDF/X files using the 2003 versions of profiles 1a and 3. |
| Licensing and patent claims | See PDF. |
| Transparency | Depends upon compliant software tools to read. Building tools requires sophistication. Encryption is prohibited in the three profiles of PDF/X published in 2003. |
| Self-documentation | Support for embedding any form of metadata for a document is extremely good. XMP metadata packages can be embedded. |
| External dependencies | PDF/X profiles intended for "blind" exchange are constrained to avoid external dependencies. All necessary fonts must be embedded. |
| Technical protection considerations | Encryption is prohibited in the three profiles of PDF/X published in 2003. |
| Normal rendering for still images | Excellent in professional tools. Third-party PDF viewers may not be able to take advantage of color management and other features intended to ensure high-quality print output. |
| Normal rendering for text | See PDF. |
| Integrity of structure | See PDF. |
| Integrity of layout | See PDF. |
| Integrity of rendering of equations, etc. | See PDF. |
| Beyond normal rendering | Annotations may be embedded. Bookmarks may be provided. |
| Tag type | Value | Note |
| Filename Extension | Assumed. The standard does not indicate that a different extension should be used to distinguish PDF from PDF/X. |
| General | The PDF/X standard is aligned to the fullest extent possible with the PDF/A standard. |
| History | TBD |
URLs
Print
• ISO 15929. Graphic technology - Prepress digital data exchange - Guidelines and principles for the development of PDF/X standards.
• ISO 15930. Graphic technology - Prepress digital data exchange using PDF. Various parts.
• Adobe Systems Incorporated. PDF Reference, Third Edition, Version 1.4. Addison-Wesley, 2001. ISBN 0-201-75839-3. Also available online as http://partners.adobe.com/public/developer/en/pdf/PDFReference.pdf.
URLs
• PDF-X.COM at DDAP (Digital Distribution of Advertising for Publications) (http://www.pdf-x.com/)
• PDF/X: Frequently Asked Questions. Martin Bailey. (http://www.pdf-x.com/downloads/pdf/pdfx-faq.pdf)
• CGATS Subcommittees. (http://www.npes.org/standards/subcommittees.html)
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