High-quality printing requires 3 to 4 times bigger image resolution as it appears on the monitor. Thus, "good looking" images on the monitor may be unacceptable in printing. For high-quality images in our book, we need to know the size of them in pixels.
In Word, images “tend to jump” to another page if e.g. we try to change their size. This is an annoying problem for longer material and there is no good solution to it.
Word does not handle transparent images well (such as png). It is more fortunate to use JPG images.
Word supports the RGB color mode and not the CMYK color mode used by printing offices. Thus, in many cases, the colors of created PDF files need to be converted, and conversion can cause unexpected surprises.
Fortunately, these conversion problems are most common in offset printing. Digital printing machines making fewer copies are more tolerant for the RGB color mode, with much less error.