Anyone tell me how to apply UCR (Under Color Removal) to my Photoshop file?
I will then be importing to a page make up program and making a print PDF for Newsprint?
In (large parts of) Europe the profile ISOnewpaper26v4 is the required one when supplying ads to newspapers.
It employs a GCR, though, as far as I know.
It’s best used for converting RGB (or Lab) images naturally, CMYK to CMYK conversions are best avoided if possible.
The old »Custom CMYK« under »Profile« in the »Conver to Propfile« dialog allows to set GCR and UCR individually, but I discourage using that as the results were not that great usually.
If you convert images to such a small color space (as defined by ISOnewspaper…) you might want to try if »Relative Colorimetric« or »Perceptual« get you better results on an image to image basis.
And if you feel the need to do additional adjustments in the CMYK image watch out not to exceed the allowed Total Area Coverage.
UCR or it's more common cousin, GCR happens when you convert from RGB to CMYK. The exact parameters of your color separation are specified in the profile that you use to do your conversion. When that profile was made, those parameters were set in the profile - black start, maximum black, total ink, etc. There is very little difference between UCR and a very light GCR in practical terms. I would just use the profile that has been recommended to you and not worry about it too much.