Adding bleed to your files is a necessary step in book printing when images or coloured backgrounds run to the edge of the page. Having a bleed area that overlaps the edge of the page prevents white borders from appearing when the books are trimmed.
As you can see above, we have a bleed applied to the image which leaves plenty of space to ensure none of the important aspects are trimmed by accident.
We recommend a page bleed of 2.5mm in most cases and this can be applied to your files by altering the size of the page, adding 2.5mm to each edge or 5mm to the height and width.
In word this can be done by selecting 'Page Layout' and choosing the 'Size' option.
Then you want to choose the paper size you are printing on and add 5mm to the width and the height. Below is an example using A4 sized paper.
You can then enlarge your images to fill the bleed area. However, please make sure that no important information appears in the bleed area as this will be trimmed off.