Yes! We can convert RGB files to CMYK easily. However, converting an RGB document to CMYK will alter the colours.
RGB colour mode can provide us with much brighter colours than CMYK mode. If an RGB document has very bright and vibrant colours, then converting to CMYK will make them appear dull.
Below is an example of a colour created in RGB . The colour is very vibrant, almost illuminant. The colour is then converted to CMYK. As you can see the CMYK colour is nowhere near as vibrant.
RGB Colour CMYK Conversion.
When converting a document from RGB to CMYK, we check the difference in colour and then send over a proof, to make this change clear.