I don't have an acrobat reader on my computer, But Adobe Illustrator can usually open any PDF file. I can definitely help if you want to check and analyze the spot colors in illustrator.
First open your PDF document in illustrator and select all of the artwork. Next open your swatches panel and to the right select the little drop-down menu and click on menu item “ Select All Unused Colors “
Next, open that drop-down menu again and click on menu item “ Delete Swatches”. This will remove all swatches from your swatch panel that are not being used in your document. Your swatches panel should now only contain the colors being used in your document and maybe a white swatch also. Notice the black swatch in this next image. It has no tiny little triangle in the corner, which indicates it is a process color.
If you double click on that Black Swatch it will open another panel, showing you it's properties
Where it says color type, you want to select the drop-down menu and choose the spot color option (if it is not already chosen) . Doing this, will ensure that any black process artwork will be converted into a spot color (which would remove any other CM or Y values). Now you will see a little triangle in the swatch which indicates it is a spot color. This is what you want
Now in this next image you will see that you can select any other artwork in your image and view it's actual percentage of the color fill.
The sure fire way though to know for sure if there is any other CMYK values in the artwork is to open your print dialog box, as in this next image. If black is the only color with the little printer icon visible, this absolutely shows there is no other CMYK artwork in your image
OR YOU COULD
Open your PDF document in CMYK color mode in illustrator and open your separations preview panel with the overprint preview option selected and toggle visibility on each one of the elements and you can see items are colored by which method