You have to convert to that color space. That means deliver a PDF/X-1a with the correct color space, not a PDF/X3 where each image has an embedded color space (and could have a different one as the others).
Best practice in InDesign would be, place images always in RGB and convert not before PDF Export to CMYK, and keep values for CMYK.
If you set your Color Setting's Color Management Policies to this:
With the Preserve Numbers (Ignore Linked Profiles) policy, all placed CMYK objects will have their profiles ignored and they will be displayed via the document's CMYK profile.
The policies are saved with the document, so for existing documents with different policies leaving Ask When Opening checked will give you the option to change policies when opening an existing document
Willi's suggestion of PDF/X-1a is probably what they want—all color in one CMYK space with no profiles. But PDF/X-1a also includes an Output Intent profile and they might not even want that. You also should know what the magazine's CMYK press profile is so you can assign it to your document, and that can be surprisingly difficult to get from many printers
Thank you so much- this clears up a lot.
So I submitted the ad just this morning with a message to the printer that I may not have done things just right - from your responses it sounds like I was about half right.
I submitted a PDF/x-1a so I know the profiles would have been ditched BUT one large image was originally Gracol 2006 coated and my settings converted to US web coated SWAP v2. So as I understand it now, the numbers would have shifted in that scenario potentially causing color issues anyway. Do you think it is worth resubmiting? This was a VERY last minute FP ad job. Absolute deadline is today.
On annother note - I put a psd file in the InDesign doc. That would not cause issue at press would it? It was one layer, CMYK.
Thanks so much for your help with this. GREATLY apreciated.
You would have less problems if you would have use RGB images. Ohterwise you have to choose between shift color or create 4 c black in text and graphics.
PSD is good, is very good.
Good file types are PSD for images, PDP or PDF images from Photoshop with vectors and/or text included, AI from Illustrator.
Bad files are EPS (because it does not support color management nor transparency), PNG because it does not support color profiles, GIF (igititititti).
JPG good when no transparency is needed, TIF ok, but has a bad preview, but when it comes to 40.000 px length on one side TIF will be the only one choice you have because that is a limitation of PSD.
PSB is not supported on InDesign on the Mac.
So as I understand it now, the numbers would have shifted in that scenario potentially causing color issues anyway.
If your document's policy is Preserve Embedded Profiles, placed images will keep their embedded profiles. If the profile conflicts with the ID doc's CMYK profile there will be a CMYK-to-CMYK conversion when you export to PDF/X-1a. The conversion attempts to change the CMYK numbers so there will be no change in color appearance.
If your policy is set to ignore profiles, images with conflicting profiles get the document profile assigned, and you might see a shift in color as InDesign shows you how the CMYK values might change in appearance under the new press conditions (SWOP vs. GRAcol).
For CMYK color, assigning or converting will create different sets of problems, it's better to plan ahead and avoid conflicting CMYK profiles, or place profiled RGB.
GRAcol and SWOP are pretty similar profiles so I don't think resubmitting will make much difference.