Is there a way to convert RGB colors to CMYK in a PDF?
I think you can in Adobe Acrobat. Open your file. Click find tools. Search “Print production.” Click convert colors. Click Device RBG under the category of Color Spaces in Document Colors. Click OK and it should work. After you click ok, you should go back into convert colors and see if it only says DeviceCMYK. If it does, your file converted correctly.