Slideshow-Exported PDF is a bit washed...

I exported my first Slideshow to a PDF file.



Looking at the PDF using the Mac Preview program the images were a bit washed out compared to the images within lightroom.



So I tried exporting some of the images to the desktop and comparing them to the images within LR and the PDF. The exported images were as vibrant as within LR. And the PDF file still looked washed out compared with them. I even downloaded the Adobe Reader and the slideshow PDF looked washed out on it.



My conclusion is that this .PDF file has images more washed out than they ought to be.



I have never created a PDF file before. Is washing out of images normal? Or am I doing someting wrong?



Thanks