How can I make a realistic text on paper just like this:
I first remove that text, and place mine, but that text doesn't appear as the original, doesn't seem realistic:
The difficult part is how to make these soft gradient and the very small grains on the edge, and toning between the shadows and the text color. Any idea how to accomplish the look seen in my first picture?
Try reducing the opacity to 90-95%, apply bit of blur to make the edges less sharp, a bit of noise to introduce some grain and make the fills less flat.
Also by editing the Layer style (right click your text layer and choose the first option) you can apply a Gradient Overlay, which (if done properly) can also add some realistic shading with the right settings.