Pixelation occurs when a digital and/or printed image has edges that look stair-stepped causing the details to be indistinct. Usually this is a result of having a
resolution lower than what is needed for the intended use. Seventy-two
dpi (dots per inch) is the recommended display on a monitor. However, when a user prints the dpi should fall in the 200-300 range.
Photoshop can surely help this using the Image Size choice to resample the image at a higher dpi.
To overcome excessive pixelation a technique called
anti-aliasing can be employed.
Anti-aliasing causes
pixels on the diagonals to fill with a color that is a transition between the pixels it lies between. This causes the edges to look smoother by smoothing out the colors.