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My colleague A used the "Save As" method to save an AI file (CS6) to PDF file.

My colleague B opened the same AI file (CC) and used "Print" to generate a PDF file.

When both PDFs were send to print digital proofs, the output colors are different, why did this happen?

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    What are the PDF Job Options when saving? Options when Printing? PPD used when printing? Document color mode? There's not enough information here to answer effectively. – Scott Jul 10 '17 at 15:43
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When you create an Illustrator file there is an option for the color mode:

  • CMYK: Cyan (blueish), Magenta (redish), Yellow, Key (black)
  • RGB: Red, Green and Blue

CMYK is a four color system used in the print industry. Comes from the days of using plates and they would have a plate for each color.

RGB is based on how TVs originally worked, where they had an electron gun for the three colours.

This means if you create an Illustrator image in CMYK (which is the default if you choose a Print profile) then when you edit it, your editing it in four color mode.

When you print to PDF, your using Windows drivers to translate the print output into a PDF file. When you save as PDF via Illustrator it will use whatever options you have chosen in the save dialog (check the Output tab, Color Conversion option). By default Illustrator will not convert when saving as PDF, so if created as RGB then will save as RGB, otherwise CMYK.

What I suspect is happening is that the print to PDF is converting to RGB when it generates the PDF, which is different to when you save as PDF which is leaving it as CMYK by default.

So check out how you created the file and the settings in the dialog when you do a save as, this will tell you what is happening.

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    RGB is how TVs STILL work (mostly) – Digital Lightcraft Jul 10 '17 at 15:02
  • Whether or not an RGB file is converted to CMYK when saving as PDF in Illustrator, depends entirely upon the PDF Job Options. And depending upon the print drivers... it's completely possible that printing to a PDF isn't doing any conversion from RGB at all. – Scott Jul 10 '17 at 15:43
  • Most print to PDF options are via third party utilities. I looked at a common one we use at work yesterday and there is no option at all to say how it will convert to PDF, so I have no idea what it is doing with the color space. The only way to know for sure is to check the settings of the file (is it RGB or CMYK) and then check the settings when doing a save as. Then compare that to the print to PDF and then it can be determined what is happening. There is no absolute answer here as there is not enough info in the question. – Metalskin Jul 10 '17 at 20:51
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There are a number of reasons that will cause the output colour to change.

The original file had spot colours, when saved or printed to pdf the option to convert spot to process was selected.

The colour profile of the artwork was changed. The original artwork was created in in SWOP, once opened the second designer chose GraCol or Fogra or whatever (without understanding what each is meant for).

Your printer (if not offset) needs to do a color calibration or your previous print was done pre-calibration.

My money is on the latter, speak to your digital printer and find out what output profile they used for the first job, if they have any kind of ripping, spooling job management software they still have that job in history and could give you that info, whether or not they know how to this is another thing.

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