In the early days of digital printing (what was then sometimes called “desktop publishing”) it was difficult for a print service provider to be able to know how a file that was submitted by a customer would print as color separations.
You could see the colors on-screen, but you couldn’t easily tell if they had specified additional ink colors that would print out on extra printing plates. So we would painfully print out separations on the laser printer in the shop.
These days, if you’re using Adobe InDesign, Adobe Illustrator, or Adobe Acrobat Pro, it’s much easier. You can use a feature usually called Separation Preview. In InDesign, choose Window > Output > Separation Preview. In Illustrator, choose Window > Separations Preview. In Acrobat X Pro, choose Tools > Print Production > Output Preview and look at the Separations pane.
You’ll see the color plates of your document as they would print out. If you move your cursor over the page, you can see the color value of the current location.
It’s particularly helpful to discover if you have more than one color specified that should be on the same color plate. In the illustration below the PANTONE 187 should be on one plate but shows up on two because the names of the plates are different.
It can save a lot of time and money to discover these problems ahead of time, before they slow things down on the printing press.