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I have to send PDF documents to a professional printing company. The company feeds back with comments about how some text should be overprinted, some logo has been incorporated in RGB instead of CMYK, and some picture having too poor a resolution.

Files being quite large, and settings sometimes being inadvertently reverted, the back and forth process to get the final document ready takes quite long, so I would like to be able to check the PDF files before sending them.

How can I comfortably perform such checks by myself under GNU/Linux ?

  • Comfortably? Buy something like the 3-Heights tools, then spend the next year or two learning to use them. – Satō Katsura Oct 16 '16 at 16:05
  • @SatoKatsura Is that sarcasm I smell there ? And why the comment when it qualifies as an answer ? Thanks anyway, I may consider this option on the long term, though of course I'd prefer an open-source solution. – Skippy le Grand Gourou Oct 16 '16 at 16:23
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    Can't really tell what you're smelling from where I'm standing. As for an open source solution, there's an entire industry out there that spent the last ~25 years making sure it's a pain in the rear to do anything useful with PDFs without their expensive tools. Now you want to undermine their collective efforts? Think of the children! :) – Satō Katsura Oct 16 '16 at 16:46
  • You might look for similar questions on our sister site graphicdesign. Publishers prefer PDF/X rather than pdf as an exchange format to obviate problems. You dont say what software you are using, but check if it has a pdf/x plugin or output. Just one step in the right direction. – meuh Oct 16 '16 at 17:08
  • @meuh I asked here rather than on graphicdesign.SE because there are very few linux-tagged questions there, so I thought the question would be answered more easily here. I wouldn't mind the question being moved, though. – Skippy le Grand Gourou Oct 16 '16 at 18:23
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As far as issues mentioned in the question are concerned (note that though these solutions may help to identify a few issues, they are limited in effiency, and are certainly not sufficient to assess the foolproofness of a PDF — see comments) :

Resolution and color space

For embedded pictures :

$ pdfimages -list example.pdf 
page   num  type   width height color comp bpc  enc interp  object ID x-ppi y-ppi size ratio
--------------------------------------------------------------------------------------------
   1     0 image    2244  2244  cmyk    4   8  image  no       215  0   301   301  418K 2.1%
   2     1 image     900   600  rgb     3   8  image  no       324  0  1524  1525 35.5K 2.2%

On Debian (Wheezy) and Fedora (23), pdfimages is part of poppler-utils packages.

For color space one can also look for DeviceRGB and DeviceCMYK inside the PDF (as a text document). It is a bit more obfuscated but it will allow to identify e.g. embedded PDF, which pdfimages will not.

Overprinting

One can look for /OP, /op and /OPM strings in the PDF source. See the 11.7.4.5 Summary of Overprinting Behaviour section of the PDF specification for more details.

The inconvenient of these methods (particularly digging through the PDF) is that objects identification may not be straightforward.

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    For what it's worth, pdfimages doesn't work with most PDFs optimized with Adobe Acrobat. With optimized PDFs raster images are split, merged, rotated, inverted etc. to allow better compression. As for locating /OP in PDFs, this can fail for many reasons. You really need an object parser for that. It really depends on how the PDF was created (and subsequently munged). – Satō Katsura Oct 16 '16 at 19:09
  • Indeed these solutions may help to identify some issues but do not seem sufficient to identify all possible issues (even restricting to resolution, color space and overprinting issues). – Skippy le Grand Gourou Oct 16 '16 at 19:27
  • My pdfimages -list output has no entries other than the header... I'm feeding it a PDF file created through Inkscape print to file feature. – ecv Jun 7 at 13:58
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You can use Scribus - it has "Preflight Verifier" tool (the icon between Print and Export to PDF) that checks for numerous issues.

You can also use it to convert PDF files into CMYK color format - when saving file as PDF, select "Printer" in the Color -> Output Intended For drop/down.

Note: I've got much better pre-flight results with 1.5.x version of Scribus.

  • As is, this answer is off-topic, since I didn't ask for CMYK but for PDF checking. However scribus actually has an incorporated PDF checking tool (the icon between "print" and "convert to PDF"). Feel free to upgrade your answer with this information. – Skippy le Grand Gourou May 29 '18 at 7:55
  • Thanks! Learned something new :) Updated the answer. How did you resolve your original issue btw? – Zaar Hai May 30 '18 at 9:25
  • Water has flowed under the bridge, but I probably stuck to options listed in my answer. At the time it didn't occur to me to use scribus' verifier. – Skippy le Grand Gourou May 30 '18 at 10:07

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