I need to save my design as a CMYK .PDF file and I have created the image in Photoshop CS6 in RGB, changed the image mode to CMYK, for black used C:40 M:40 Y: 20 K:100, and when saved the file as a Photoshop .PDF- it opens in Adobe Acrobat Reader looking washed out and grey. I only used three colors (black, white, and red) and the black is the most noticeably greyed out. The red also looks slighty washed out. But the weird thing is- when I open the .PDF in Photoshop, all the colors look right.
I've tried googling this and messing around in Photoshop and Adobe Acrobat Reader all day and just can't come up with a solution.
I don't know a lot about this kind of stuff so I'm really lost. I really need the file to be the right colors in .PDF. Please, can anyone help me? 
Below is a comaprison image of the design .PDF file opened in Photoshop versus opened up in Adobe Acrobat Reader:
This is truly driving me crazy.