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  1. Using InDesign I created the interior of a 352-page book. It is supposed to be black only. But some of the diagrams in the book have hidden CMYK values.
  2. I created a PDF from InDesign. The PDF retains the hidden CMYK values.
  3. How can I convert my PDF into one that is black ink only, with no CMYK or color values? Is there a simple way to do this in Acrobat?
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Can do:

  • Tools -> PDF Standards -> Preflight -> Convert to Grayscale

or

  • Tools -> Print Production -> Convert Colors -> Conversion Profile -> Pick the one you want
  • 1
    I would check after if the values are converted to K100%. – Rafael Sep 4 '15 at 18:56
  • Thank you! This Preflight > Convert to Grayscale is by far the easiest. – wernermischke Sep 4 '15 at 19:06
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Ideally, you would alter the images placed in InDesign using their native applications - Photoshop/Illustrator - then replace them (or update the links to them) in the InDesign layout and regenerate the PDFs needed.

Conversion to Grayscale from CMYK can often result in various percentages of black and rarely will result in 100% black if that's the desired percentage. The only way to ensure 100% black is 100% black is to make certain the original artwork is set to use that color and percentage.

  • While that's a good rule for quality, it won't necessarily result in a grayscale PDF. Complete grayscale is often required in to avoid color clicks on the printer. So, even if Wernermischke were to go through the trouble of converting his images to grayscale, it would be useless if production required trim marks or page information, which appear in Registration black, which would trigger the color click. The most sure-fire way to prevent unnecessary color clicks is to somehow generate an entirely grayscale PDF, OR (if the RIP supports it) to configure the print job to run in black only. – 13ruce Sep 4 '15 at 20:31
  • Marks are irrelevant. I suggested altering the original images not the PDFs In most instances converting CMYK to greyscale results in a tint of black. Which is fine if that's what you want. But if your desire is to get 100% solid black, converting from CMYK to grayscale will almost never accomplish that. – Scott Sep 5 '15 at 0:38
  • I disagree. Marks and page info are perfectly relevant considerations if the goal is to prevent color clicks. Registration black is not simply 100% black, but 100% of all colors. So converting the source images to grayscale will result in the best quality output, but unless the PDF is ALSO exported to a grayscale format (or converted later) the machine will often still record a color click due to the trim marks and/or page info. – 13ruce Sep 8 '15 at 11:37
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You can do this really easily by using the preflight option in Acrobat. In the 'Prepress, Colour and Transparency' fixes menu, search for 'Correct 4C Black' - this will identify any 4C black in your document and then change it to 100% K

You can specify if it's text and vectors, vectors, just text, images, etc. you want changed as well, which is great.

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You don't have to do it as an extra step in Acrobat. You can create the PDF in grayscale to begin with by "printing" to the Adobe PDF driver with "Composite Gray" selected in the Output tab of the Print Dialog.

  • The Adobe PDF driver died in roughly 2002. No user in the past 12 years has had the Adobe PDF printer drivers installed. While this answer was valid a decade ago, it's invalid at this time. – Scott Sep 4 '15 at 19:49
  • While one may have access to the latest release of CC and Acrobat, many still use Acrobat X, which installs the PDF printer driver. So it's not quite so old as that. Many of us with heavy investments in plugins hang on to legacy versions of the host platform in order to mitigate the cost of upgrading for no significant benefit. It's not at all uncommon for users to be running vintage releases for perfectly legitimate reasons. At any rate, it doesn't have to be the Adobe PDF printer. There are free contemporary pdf printer apps out there that could easily accomplish the same effect. – 13ruce Sep 4 '15 at 20:14
  • Acrobat X does not install the PDF driver. The last version to install that driver was Acrobat 8 I believe (may have been 7 or 9 though, definitely not Acrobat X.) While you can manually install the driver. It is notoriously old and problematic, which is why Adobe dropped it. – Scott Sep 4 '15 at 21:08
  • Thanks for the correction. However, as I said, there are contemporary PDF printers available that can accomplish the same goal. – 13ruce Sep 8 '15 at 11:40

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