You'll have to be way more specific.
Start with what version of Acrobat you're using. Do you have Acrobat Pro or Acrobat Standard? What color do you want to replace with what color? Do you want to do this globally or for a specific object?
If you have a recent version of Acrobat, the two main tools would be Preflight and Convert Colors.
I using Acrobat Pro and want to replace the CMYK value of an object or text throughout the whole document. Say text is 100 cyan 50 magenta can I replace it
with 80 cyan and 30 magenta throughout document
I've used Acrobat Pro to convert a CMYK value to spot, but it looks like the same Fixup can be used to convert CMYK to CMYK.
Open Preflight (must be Acrobat 9 Pro or Acrobat X Pro). Click on the Fixup button at the top of the dialog. From the Preflight panel Options menu, choose Create New Preflight Fixup. In the the Fixup Category : Color spaces, spot colors, inks, select Convert to Spot Color.
In the bottom section, the Source Color can be specified as CMYK values. Enter the starting CMYK values.
In the Alternate Source menu, you can choose CMYK instead of spot. Enter the CMYK values you want to change to.
Click OK. You'll be asked to save the file under another name (it's being permanently changed).
Works for spot colors. Should work for CMYK. One color at a time.
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