Converting a RGB pdf to CMYK while preserving vividity

Hi there

I've purchased Pro because I undertood that it might be able to help preserve the vividity of an RGB pdf when I convert it to CMYK

The original file was created in Canva but when I export it there to a CMYK pdf for print it goes really dull (the original image has bright striking blues). So I've tried exporting it as an RGB pdf (which looks perfect), then importing that  to Pro and then using Print Production (potentially incorrectly ) to output it again to a CMYK pdf.

But it makes no difference ;-(

I'm hoping someone in the community might be able to suggest a solution.

It's for a book cover and the current colour output colour is hugely disappointing

Help!

Many thank s