This happens when you colour manage CMYK to another CMYK space, try using the PDF X/1a setting first and make sure Preserve Numbers is set for output, let us know how that goes.
In the PDF export options, go to
Convert to Profile (preserve numbers)
thank you that was the problem, the document was in a slightly different colour space to the output. so even with 'preserve numbers' selected it was messing them up. i still don't understand why it would do that on the linked files, but be ok with the straight export though? (they all have the same set-up!)
i still don't understand why it would do that on the linked files, but be ok with the straight export though? (they all have the same set-up!)
The rules for placed InDesign files are the same as for images and other placed assets—if there's a conflict between the assigned profiles and the output or export destination profiles there will be a conversion to new color values.
The Convert to Profile (preserve numbers) option in PDF Export only preserves the CMYK values of the document's objects (not placed links) when there's a conflict. If you want to protect the numbers of placed files, your document's CMYK Color Management Policy has to be set to Preserve Numbers (Ignore Linked Profiles). The policy is set when the document is created.
So you might have a case where you want to force the conversion of all the images in a document into a different final CMYK destination, but want to keep the CMYK values of InDesign's type and fills unchanged. In that case you would need a CM policy of Preserve Embedded Profiles and a PDF Export>Color Conversion of Convert to Profile (preserve numbers).
If you wanted all of the numbers preserved and simply wanted to assign a new CMYK profile on export, then the CM policy would have to be Preserve Numbers (Ignore Linked Profiles) and the PDF Color Conversion would be Convert to Profile (preserve numbers).