Who makes the PDF?
It's quite easy to define a Preflight profile in ID to flag RGB colors, and you ought to be able to convert colors to a specified CMYK profile automatically on export if you are using the right settings.
Mostly it sounds like whoever is making the PDFs needs to set up an export preset to convert color to the printer's specified profile.
Thanks for the reply. Unfortunately I haven't been able to get the printer's profile from them, otherwise that would be the best option. I hadn't realized the [Basic] Preflight settings aren't set to flag the RGB options. Now that i know where to look, it's easy to set that up to flag them.
Thanks for the help.
Quite often you can find the appropriate CMYK profile for publications online with their advertising technical specifications, and they often use industry standard ones. Once you have that, you can assign it to your InDesign documents, and convert any non-CMYK content to it when you export to PDF.
Or, you can settle for standard ones (like FOGRA39 in Europe, or SWOP in America), but that could be risky, especially with newspaper ads.
Unfortunately I haven't been able to get the printer's profile from them, otherwise that would be the best option.
If you find RGB objects what will you do with them? The conversion to CMYK will require a profile no matter where you make it, so if you find an RGB swatch or image and change it to CMYK the conversion is via your document's CMYK profile. You'll get the same result if you leave the swatch as RGB and set the Output Destination to Document CMYK when you export. Both the PDF/X-4 and X-1a presets let you do that.