We make quite a lot of mood boards in InDesign, which we then export as CMYK PDFs (Document CMYK - U.S Web Coated(SWOP) v2) as the image below. We then send them off to the printers to be printed on A2 photo paper and mounted onto foamboard.
What I've noticed is that the colours in PDFs come out rather dull (on the screen and in print) when compared to how I would normally do them. Is there any reason for this and is there any way I can fix it?
The CMYK color space is different than the RGB color space, so you loose certain colors you had in RGB if you convert to CMYK. These tend to be the more vibrant colors.
I'd suggest a) not converting at all and leave them RGB or b) make sure you are getting the right color profile for the particular printer that's being used and use that for the conversion.
With option 'a' the idea is that, while it will still be converted at some point, it will be converted by the printing software, which maybe will do a better job than the profile you have in the PDF file.