Here is a quick way to take any shape, object or text and create a darker slip shadow like you see in some illustrations and infographics.
Start with a simple shape. Filled with a color but no stroke around the object.
With the object sleected with the Selection Tool, hit the return key to bring up the Move dialog box. Set the H & V to ZERO in each field and press COPY. This duplicates the shape on top of itself, very important.
With the duplicated shape, hold OPTION + SHIFT and click and drag the shape. Holding shift allows the shapes to be dragged at a 45° angle.
Select the first duplicated shape and the last duplicated shape and choose Object > Blend > Blend Options... and choose Specified Steps from the drop-down menu. Set the number of steps. In this case I moved the object about 2.5 inches so I chose 250 steps. 4 inches would be 400 steps.
Once the Specified Steps are set, choose Object > Blend > Make. This will blend the first and last object together with 240 steps or duplicate shapes.
Here is the result of 250 shapes blended together.
To make this into a single shape, choose Object > Expand.
The Expand panel will open, click OK.
With the Blend Expanded, choose Unite in the Pathfinder Panel to combine all the 250 shapes together into one shape
Send the object to the back by choosing Object > Send To Back. This put the "shadow" to the back behind the original shape.
Change the color of the shadow to a lighter or darker color to show the slip shadow behind the original image.
Putting it on a similar color background adds to the effect.
When using a font, make sure to outline the type before performing the same steps outlined in this tutorial.