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PDF FOR THE GRAPHIC ARTS
Creating and preflighting PDF/X-1a files is invaluable for the graphic arts professional. It greatly improves the reliability and efficiency of their document delivery.
The PDF (Portable Document Format) file format was created by Adobe Systems in 1993. It allows formated documents to be viewed (and printed) independent of the application software, hardware, and operating system. PDF files contain a complete description of a fixed-layout 2D document which includes the text, fonts, bit-map images, and vector graphics making up the document.
PDF is a versatile format that’s supported by the majority of todays applications. Unfortunately this means it’s very easy to create PDF files completely useless in a prepress environment.
The solution is to define a set of rules that don’t allow use of certain PDF functions that serve no purpose in prepress. Several industry organizations have been working together for many years and the result is the PDF/X standard.
The PDF/X standard is independent of the platform, operating system, or software application used and is designed for blind exchange of print-ready pages. This ensures graphic arts files are written in a way that will reproduce on press exactly the way the content creator intended.
What is PDF/X-1a?
PDF/X-1a files are now an official ISO standard (ISO 15930-1) They’re regular PDF 1.4 files which have these restrictions:
- Fonts must be embedded in the file.
- Color data must be grayscale, CMYK or named spot colors. RGB, LAB, and other similar data are not allowed.
- OPI is not allowed.
- Files cannot contain music, movies or other non-printable content.
- Annotations, such as “sticky notes” should be located outside the bleed area.
- Files may not contain forms or Javascript code.
- A limited number of compression algorithms are supported.
- Files cannot be encrypted.
- Transfer curves cannot be used.
In addition to things not allowed, certain information needs to be present in a PDF/X-1a file not usually found in regular PDF files:
- A “flag” indicating whether the PDF/X-1a file is trapped or not trapped.
- Information defining the bleed and trim area.
MediaBox defines the size of the entire document
ArtBox or the TrimBox defines the extent of the printable area.
BleedBox must be defined if the file is to be printed with bleed. It must be larger than the TrimBox/ArtBox, but smaller than the MediaBox.
- The file must contain an output intent describing the intended printing condition. The output intent is either:
…an ICC color profile (embedded or referenced).
…an output condition identifier (a text description of the intended print specifications).
- A flag indicating the PDF file is a PDF/X file and which type of PDF/X file it is.
Just the starting point
With all the restrictions just described, you’ll be guaranteed perfectly printable files every time.
Think again.
A good example are photographs. There are no rules in PDF/X that state images need to have a certain resolution. A file with 50 dpi images can be a valid PDF/X file. Unfortunately the printed result would be unacceptable if used for printing a glossy magazine.
Creating PDF/X-1a files
Many of today’s graphics applications can produce PDF/X-1a compliant files. Another solution is purchasing Adobe Acrobat. Version 7 and later have PDF/X-1a support built into Acrobat Distiller, the module used to create PDF files. For converting existing PDF files to a PDF/X-1a files, Adobe Acrobat Professional has a plug-in that can be used.
Why should you use PDF/X-1a?
By using PDF/X-1a compliant files, you won’t have to worry about being asked to supply missing fonts or images. You will never have to be concerned about images being converted from RGB to CMYK. Whether or not the printer should trap your file will be based on reliable information. Last but not least, your printer will know if your file was properly prepared for the press it is supposed to print on.
A PDF/X-1a workflow not only gives you confidence your print-ready files will reproduce as you intended, you will also save time and money. Documents returned because they weren’t properly prepared requires additional time to correct. This additional time costs money which you either abosrb or the client pays for. Adoption of PDF/X-1a can significantly reduce and possibly eliminate such additional expenses.
A far more serious concern, from a business point-of-view, is when a poorly prepared document doesn’t get returned. Failing to meet a client’s expectations often means losing that client.
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