Problem: Resampled low-resolution image doesn't look its best.
Solution: Use sharpening.
Resizing a low-resolution image to make it smaller is easy. Resizing a low-resolution image to make it larger is more complicated because resampling is necessary to gain enough resolution for printing. Resampling isn't a bad word, but it can lower image quality. The key is to be conservative. You can only push an image so far before it starts to look bad, so you might not be able to turn a 72 ppi image into ...