Start Smart: Create Quality PDFs
This story courtesy of Blueline, the quarterly newsletter of the Printing Industries of Northern California (PINC).
What makes a “quality” PDF? As it relates to print production, a quality PDF contains all of the necessary items to print a job successfully on press.
An interesting statistic is that many of the same problems associated with native application files years ago are the same problems seen in PDFs today. In an ideal situation, the PDF file is created from a professional desktop publishing application such as Adobe InDesign or QuarkXPress.
Remember that a quality PDF begins with a quality native application file — making sure that it contains bleeds, images with adequate resolution, images in the correct color space, quality fonts, and spot colors named properly.
Dealing with Images
The most common problems associated with PDFs are images that are in the wrong color space, images that contain inadequate resolution, and images that have been over-compressed. A native file containing images with proper resolution ensures that they will print crisp and sharp, with no loss of detail.
To determine proper resolution, use the “two times” equation. This means that the resolution of the images (pixels per inch, or PPI) must be twice the line screen (lines per inch, or LPI) in which the job will print.
Images with too much compression applied will also affect print quality. The two most commonly used compression methods are ZIP and JPEG. ZIP compression is lossless and will not affect image quality whatsoever. ZIP compression works well with imagery that contains large areas of solid color.
JPEG compression is lossy; meaning loss of image quality will occur. Although this sounds ominous, a low JPEG compression setting (or maximum image quality) can be used with little or no noticeable image degradation.
Images must be converted from the RGB color space to CMYK for print production. This conversion process is more than just a mode change in Photoshop. Considerations must be made for paper type (coated or uncoated), dot gain, and total ink coverage, to name a few.
The best policy is to request a color settings file from your print service provider, then load that color settings file into Photoshop. If your service provider is unable to provide you with a color settings file, the next best option is to select North America Prepress 2 (Edit > Color Settings in Photoshop under the Settings pull-down menu).
Fonts and More Fonts
The ability to embed fonts within a PDF is one of the format’s greatest strengths. When fonts are embedded in a PDF, a compressed, encoded set of glyphs (characters) will be included in the file. Be aware, however, that some fonts contain licensing restrictions; this means that they cannot be embedded in a PDF!
If you’ve obtained fonts from an obscure font foundry or from a “freeware” site, it’s always best to make sure that it can be embedded in the PDF. This can be tested simply by creating a page that contains the font, then exporting a PDF. A warning dialog box will display immediately during the PDF creation process if the font cannot be embedded. Remember, the last thing you’d want is to design an entire document only to find out you can’t create the PDF because a font that was used contains an embedding restriction!
Make It Bleed
Missing bleeds in a PDF is another common problem. While missing bleeds can be fixed easily in the native application, repairing bleeds in a PDF can be a time-consuming process for your print service provider. Make sure that adequate bleeds are created (typically 1/8″) in the native application file and that they are included in the resultant PDF.
In the export PDF dialog found in QuarkXPress and InDesign, there are options to include bleeds. Typically, the options are symmetric (same bleed amount on all page edges) or asymmetric (define different bleed amounts for each page edge).
Spot or Process?
Defining color properly in the native application is a critical step in creating quality PDF files. If the document contains spot colors that will print as additional inks on press, make sure that they have not been converted to process in the native application. Again, correcting this within PDFs is a very time-consuming procedure for your print service provider.
Work with Your Service Provider
Finally, the last consideration for creating quality PDFs is to work closely with your print service provider. One of the best things you can do is ask for the Adobe PDF Settings that they recommend for creating PDFs for print production. The Adobe PDF Settings file is shared among all Adobe CS applications and can be found in the following locations:
Mac OS X (Acrobat 7): Library > Application Support > Adobe PDF > Settings
Windows (Acrobat 7): Acrobat > Distiller > Settings
Remember, a properly created PDF file is the cornerstone of the print production process. By taking the time to prepare your native file carefully, and using quality PDF settings to create a PDF file, you will be on your way to a successfully printed job.
To obtain a set of tested, quality Adobe PDF Settings for print production, send an e-mail to jm****@*****tf.org.
Joseph Marin is the senior prepress technologist/instructor at PIA/GATF. Tracey Ryan is a graphic designer at PIA/GATF
Reprinted from PINC Blueline #75 Winter 2007.
This article was last modified on January 10, 2022
This article was first published on March 2, 2007
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