Creating a PDF document for printing is different from making a PDF for the web or emailing your friends and colleagues. Even PDFs used for presentations on a projection screen deliver a vastly different look when you send them out for printing.
If you are having the pages bound, you have to set up your PDF files so the area to be bound, called the gutter, does not have any text or pictures. If you do not allow for this area, your readers will not be able to read some of the text at the edge of the page near the binding. Also remember that odd and even pages have this gutter area on different sides of the page.
Text placement can also be too close to the edge of the page opposite that of the binding. Remember that your 8-1/2” by 11” page will become 8-1/4” by 10-3/4” once the page is trimmed. The trim lines are situated 1/8” from the top and bottom of the page, as well as ¼” from the outside edge opposite from the binding.
Now, for esthetics, you should allow for comfortable borders measured from the trim lines. This makes for easier reading and a professional look. If you have charts, graphs or pictures, make sure these are also within the trim lines. Leave some plenty of border space to make the charts and pictures just pop and draw the attention of the reader.
Background graphics or pictures that extend to the edge of the page are a different story. You will need to treat these differently than you handled the text. Here is why: When a book gets printed, a paper shear cuts the pages along the trim lines. Sometimes the shear is a little off or the paper shifts slightly and you will get a thin white line running along the edge of your picture.
In order to prevent this from happening, position the picture so it crosses the trim lines into the parts of the page that will be cut off. These areas are also called the bleed area. You picture should “bleed” into this area so a misalignment in the trimming process will not be noticeable.
Picture via Webcomics Community Forum