Photoshop offers many ways to make text look old, like it came from an old typewriter. Several fonts available for purchase were created specifically for this purpose, but the consistency in those fonts marks them as being a modern imitation. Using filters on a layer mask creates authentic-looking worn type full of variations in apparent wear, and there is no need to buy and extra font. The font "Courier New" works best for this process because it is a common typewriter font.
Press "T" to enable the text tool and type the text you wish to transform.
Press and hold the "Control" key and click on your text to select it.
Click the "Layers Mask" button at the bottom of the layers palette. You should see a thumbnail image of the layer mask in a box beside the "Text Layer" symbol. Keep a solid line around this thumbnail or you may end up altering the actual layer instead of the layer mask.
Click the "Filter Menu" and select "Brush Strokes." Choose "Spatter."
Set the "Spray Radius" and "Smoothness" settings each to "10" or adjust the setting to your liking. Click "OK."
Click "Blur" under the "Filter" menu and select "Gaussian Blur." Adjust the setting to "0.3" or experiment to find a look that works best for you.
The "Sprayed Strokes" filter creates a similar worn effect. The preview function will show the text as much more severe than the final product will be. This is because you are altering the mask instead of the actual text.