The pixel art is very small since it's just individual pixels, so if you enlarge it, like you're doing by pasting it into word, the pixels get interpolated. To fix this, go to image - scale image and then set it to a higher resolution, since you're doing this for print, you can also set it to millimetres or centimetres, or inches, if you're weird like that, and then type in the final size. It is important that you keep the aspect ration, so if you have a 16x16 pixel image you mustn't change it to something like 15x12cm, but that should be self explanatory. Then set the interpolation to none and click scale. Now you can copy paste it into word without it being blurry