PDF/X Files and Adobe Creative Suite 3

The PDF/X standard

The PDF/X standard responds to the challenge of ensuring that graphic arts files are written in a way that will reproduce on press exactly as the files’ creators intended. This simple sounding, yet daunting goal requires successful “blind” communication between two or more production tasks across a plethora of platforms, operating systems, software applications, color spaces, font types, file formats, and media. (Blind communication or exchange means that the file is thoroughly validated, so that a provider can “blindly” accept it.) Over many years, several industry organizations have developed the PDF/X standard—actually a set of standards—to meet this goal.

A subset of the Adobe PDF specification, PDF/X is designed for the blind exchange of final print-ready pages, and is one of the most predictable ways to deliver files bound for press. PDF/X-1a and PDF/X-3 are the most popular PDF/X formats; PDF/X-4 is a new standard, ratified as a CGATS (Committee for Graphic Arts Technologies Standards) and ISO standard in 2007. Adobe Creative Suite 3 supports all these PDF/X standard formats.

Using PDF/X-compliant files eliminates the most common errors in file preparation: fonts that aren’t embedded, incorrect color spaces, missing images, and overprinting and trapping issues. These issues don’t arise with PDF/X files because, by definition, these standards require that all fonts be embedded, appropriate PDF bounding boxes be specified, and color be correctly and consistently defined. PDF/X-compliant files also must describe the printing condition for which they are prepared.

If you send PDF/X-compliant files, you won’t have to worry about being asked to supply missing fonts or images. Nor will you have to be concerned about a service provider converting an image from RGB to CMYK without your seeing the results. And, the printer will know if the file was prepared properly for high-quality print output.

Many creative professionals prefer to prepare all the PDF files they will submit for printing in the PDF/X format, even when the print provider does not specifically require it. The PDF/X format is an efficient way to ensure that a file is validated against industry standards for high-end printing and is print ready.

Choosing a PDF/X file format

PDF/X has three variants, PDF/X-1a, PDF/X-3, and PDF/X-4; in some cases, a specific variant has different versions. Each variant has an arena of use, depending on the kinds of files you work with and the workflow you require; all variants share the PDF/X advantage of consistently describing a “reliable PDF file for print.” But as with any printing options, you lose some flexibility when you gain greater control.

When deciding which PDF/X variant to use, in general:

Choose PDF/X-1a when CMYK files are required; you’re sending digital ads to be reproduced on a press characterized to a printing standard such as SWOP (Specifications for Web Offset Publications) or SNAP (Specifications for Non-heat Advertising Printing); or when you want to maintain absolute control over a file’s content and color appearance.
Choose PDF/X-3 if your workflow requires transferring data in CIELab or RGB color spaces, with conversion to CMYK occurring later. Use PDF/X-3 for complete files that you will send to digital presses or other color-managed environments, or for some digital ads, where you expect the printer to optimize color reproduction for the specific printing environment.
Choose PDF/X-4 for printing artwork with live transparency and layers. Expected to be ratified as a standard in 2007, PDF/X-4 supports transparent artwork and effects, as well as layers. Print workflow systems based on the Adobe PDF Print Engine can process PDF/X-4 jobs natively, without flattening artwork or converting the file to PostScript.

Note: CS3 and Acrobat 8 users can take advantage of print workflow systems and RIPs powered by the Adobe PDF Print Engine. This technology allows PDF documents and jobs to remain unconverted and independent of printing devices throughout a print workflow. The technology, for example, eliminates the need to flatten transparent artwork and effects to ensure accurate and consistent reproduction of complex artwork, in all stages of the production process—print preview, proof, and print. For the first time, prepress and print production tasks now can be done using the same technology in Adobe applications—such as PDF rendering libraries and color management systems. Products based on the Adobe PDF Print Engine are available through Adobe print OEM partners. For more information on the Adobe PDF Print Engine, visit www.adobe.com/products/pdfprintengine/.

Table 1: PDF/X file formats available in Adobe Creative Suite 3 components

PDF/X format	Contents	Use	Standard	Compatibility	Transparency support on output
PDF/X-1a	CMYK colors, named spot colors. (No RGBor device- independent (color- managed) data.)	Blind exchange of documents; streamlined and validated for use in high-end press workflows.	PDF/X-1a: 2001	Acrobat 4.0/ PDF 1.3	Transparency must be flattened
PDF/X-1a			PDF/X-1a: 2003	Acrobat 5.0/ PDF 1.4	Transparency must be flattened
PDF/X-3 (All PDF/X-1a files meet the requirements for PDF/X-3 files.)	CMYK, spot, calibrated RGB and Lab colors, ICC-based color.	ICC color- managed workflows. ICC color profiles are included in PDF/X file. Allows RGB images that include enough information to be treated as device- independent.	PDF/X-3: 2002	Acrobat 4.0/PDF 1.3	Transparency must be flattened
	CMYK, spot, calibrated RGB and Lab colors, ICC-based color.		PDF/X-3: 2003	Acrobat 5.0/ PDF 1.4	Transparency must be flattened
PDF/X-4	CMYK, spot, calibrated RGB and Lab colors, and ICC. Can contain live (unflattened) transparency and layers.	Color- managed workflows and workflows using Adobe PDF Print Engine. Transparency in artwork stays live.	PDF/X-4: 2007	Acrobat 7.0/ PDF 1.6	Live transparency and layers supported

About PDF/X file contents

PDF/X files require certain contents, prohibit others, and leave some open. It’s helpful to know what’s allowed and prohibited in PDF/X files before creating, preflighting, and correcting them; and when customizing any settings. See Best practices for creating valid PDF/X files for additional guidelines on contents.

Here’s what must be included in a PDF/X file:

Fonts and images embedded.
Page geometry (the trim box and bleed box) defined.
Intended printing condition (output intent).
Trapping key (Yes = True, No = False) defined.
Title, creator, producer, creation, and modification dates.

Here’s what’s prohibited in PDF/X files:

Live transparency, except in PDF/X-4 files.
Layers, except in PDF/X-4 files.
Encryption (security).
Form fields.
Interactive elements including movies, sounds, buttons, and hyperlinks.
Annotations within the bleed box.
Preseparated PDFs.
Transfer functions.
Actions and JavaScripts.
Embedded PostScript®.

PDF/X files do not set a minimum image resolution nor limit the plates used.

About the PDF/X standard and transparency

Originally released in 2000, PDF/X standards continue to evolve, mainly with the wide adoption of newer versions of the PDF specification. Here is the evolution of these standards and how they handle transparency in files:

The PDF/X-1a:2001 and PDF/X-3:2002 standards are based on PDF 1.3 (Acrobat 4.0). Creating a PDF 1.3 file—such as from InDesign CS3, Illustrator CS3, or Photoshop CS3—flattens transparency.
The 2003 versions of the PDF/X standard (PDF/X-1a:2003 and PDF/X-3:2003) are based on PDF 1.4 (Acrobat 5.0), but can also accommodate PDF 1.3 files. This standard does not support transparency. You can still use transparency in your design, but you must flatten the transparency before creating a PDF/X-1a or PDF/X-3 file.
The PDF/X-4:2007 format saves PDF 1.6 or later files. This format preserves transparency (does not flatten it) and layers.

In general, it is best to leave transparency live in artwork, until the end of the workflow. If flattening is necessary, a print provider can use the appropriate flattening resolution at print time. Discuss these PDF/X file formats with your print provider or the publisher you will send files to, and use the format and settings recommended.

PDF 1.4 and later files support live transparency, but until the PDF/X-4:2007 standard, PDF/X files did not. Thus, you can save a PDF 1.4 file from InDesign, Illustrator, or Photoshop, and any transparency remains live; but the resulting PDF 1.4 file is not a valid PDF/X file. For this reason, CS3 components create PDF/X files in PDF 1.3 format, as valid PDF/X files, with properly flattened transparency.

CS3 and Acrobat 8 support all PDF/X formats (PDF/X-1a:2001, PDF/X-3:2002, PDF/X-a1:2003, PDF/X-3:2003, and PDF/X-4:2007). CS3 components create PDF/X-1a:2001, PDF/X-3:2002, and PDF/X-4:2007 versions by default.