Step 1
Create a small document. I made mine 25x25. Zoom nearly all the way in. First, get your pencil tool and set it to a hard brush at 1px wide. Set your foreground color to black and draw a rectangle as seen in the picture. make sure there is a cut near the top left. Remember to stick with straight lines only.
Step 2
Now create a new layer and draw the folded portion of the page near the top left.
Step 3
Make a new layer and select the space inside of the file. Fill it with any color and double click it to get to its layer style. Apply a Gradient Overlay. make sure you use LIGHT colors. I chose a very light orange for the bottom color and white for the top color.
Step 4
Create a new layer and add some straight lines inside the file. Set the opacity to 50% and you're done!
Final Result:













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