From a printing industries point of view, not all PDF's are created equal. When it comes to commercial printing, some PDF files actually print better then others. So if there is a difference, what makes one PDF print better then the others?
To answer that question, let us take a look at three popular PDF file types, internet, digital proof, and press-ready PDF files.
Internet PDF Files
For the most part, PDF files found on the internet are the smallest, most compact in circulation. They have vastly reduced image data, and sometimes no fonts at all, to keep the file size small. This is great for passing around information electronically, but is not the best resource for offset printing.
When PDF files do not include fonts, prepress departments usually cannot process them at all and the file will generate an error that halts digital processing. Therefore, this type of PDF file cannot be printed by most commercial offset printers.
Additionally, many copyrighted articles and publications are published on the internet in a PDF format with password protection. This enables viewers to read them on a computer screen but cannot be reprinted by a commercial printer -- to preserve the copyright.
Digital Proof PDF Files
Creative professionals commonly use PDF files as digital proofs for their clients. Digital proof PDF files are commonly emailed, and therefore are a reduced file-size version. Furthermore, for viewing purposes, the pages are cropped to the actual page size without the use of crop marks or bleeds. After approval, these PDF's are often mistaken for being press-ready, but need to be considered with caution.
Typically, there are three common problems that may be encountered from using digital proof PDF's for offset printing. First, any spot colors present in the original file will be converted to RBG or CMYK equivalents when the PDF is being generated, which can alter the intended use of spot color inks on press. Next, any pages where colors or images touch the page edge will need to be altered to extended beyond this point. Finally, images in the PDF may be greatly reduced in image resolution; therefore, appear to be less detailed than the original version.
It would also be important to note that many software applications only create proof quality PDF files. If your layout program does not give you the option to select a PDF type, or change the settings, the resulting PDF will be equivalent to a digital proof.
Press-Ready PDF Files
In order to generate a truly press-ready PDF file, it is necessary to properly prepare your files for press, to compensate for issues that may occur during print production. Since a PDF must meet certain criteria in order to properly print on an offset press, setting up the digital file with this in mind is a necessity. Some of the issues that are important for the commercial printer are proper page setup parameters like number of pages, page-size, margin and bleed considerations. Other issues are font usage along with various image considerations including, resolution and color type.
In order to generate a press-ready PDF that allows for and considers the topics discussed above, it is necessary to use applications that can generate a press-ready PDF such as Adobe® Acrobat Distiller®, or professional layout programs such as Adobe InDesign® or QuarkXPress®. All of which give you settings, or parameter options, for PDF creation that preserve the integrity of the original document for offset printing. This will include the necessary image resolution, font information, and preserve proper color separations.
While we discussed three very different types of PDF files, there is one specific type that works best for commercial offset printing. By submitting press-ready PDF files to your favorite printer, instead of digital proof or internet PDF files, you can potentially save yourself time, money and even frustration.
Jack is currently a prepress manager and member of the PrepressX team, who are actively developing a prepress resource website for the printing and graphics community.
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