Understanding bleed & safe

The bleed inflate represents an extra bit of padding added to the trimmed dimensions of your page. It is the area that is cut off the page after it is printed - this ensures that if the cuts are not 100% accurate, the trimmed page won't have a white unprinted line at the edge. Rendered files will show cropmarks precisely on the line between the trim and bleed. Anything past the trim line is not expected to make it into the final printed, trimmed and bound book.

Safe inset are arbitrary guidelines that help the placement of images and text on the page so that they are not occluded after binding. Consider it a very useful page margin, designed to keep meaningful content away from the binding gutter, and to ensure that content doesn't get trimmed off if the paper is cut a little too tight at the edges.

Bleed inflates and safe inset guidelines are set at the requirement of the specific printing & binding equipment used to make your books. Some printers will use precut sheets, so a bleed may not be necessary. Other printers require the use of impositioning software to arrange multiple pages on an uncut sheet, with different tolerance levels for cutting precision. There are many different collation and binding techniques, some of which obscure more of the page in the gutter. Covers may need extra dimension to wrap around the edges of the page. Each situation is unique for your printing process.

With all these choices, the best resource for answering questions about your book product sizes are people who do the imposition, printing, trimming and binding of your books. If you have questions about setting up your product sizes, ask your printing technician - they will be able to tell you what is required to get best results for your clients books on their equipment.