Folding, Creasing cutting and trimming, Binding

To produce a book, pamphlet, report or brochure, flat sheets are folded either on machine (web presses) or on a folding machine in the "Finishing" Department. Both gate and buckle folders are used. Sheets are folded into sections in multiples of 4 pages, so sections can be 4,8,16,32 up to 64 pages.
Paper up to 170 gsm can normally be folded without the need to prescore. When heavy weigh papers are used in books parent sheets may be halved or quartered before folding to minimize the thickness at the fold.

It is recommended that stock of 170 gsm and above be scored or creased before folding whether being folded as a cover, a section or a 4-page folder. In common terminology scoring takes place on the folder by a set of top and bottom male and female rollers, creasing takes place on a flat bed or rotary cutter and creaser using scoring rules and matrix.
In creating a score by both methods an internal bead is created on the inside of the fold by delaminating the internal structure of the board or paper.

The width and depth of the crease increases with the thickness of the product.

Things to watch out for.
Cracking on the outside of the fold.
Cracking is much more evident when a solid print covers the fold line. It is recommended to keep printing on the fold to a minimum.
On heat set web offset this may be caused in lightweight papers by over drying in the oven after printing but before folding. Some web machines allow for remoistening before folding.
On gloss coated sheets heavier coating weight stocks are more liable to crack, as coating is less flexible than the base paper.
Higher gloss art papers are more likely to crack because of the super calendaring, process that imparts the high gloss.
Paper that is dry either by manufacture or exposure to low humidity is more likely to crack.
Folds across the grain crack less than those along the grain.
Special purpose Art boards are designed to maximize creasing and folding but may not have the printability or gloss required for the job.
If it is imperative that there be no cracking on the fold film lamination is recommended.

Binding
Binding is the term for attaching sheets or folios of paper so as to form a book, report or brochure.
Most common types

Saddle stitching
Side stitching
"Perfect" binding, (adhesive binding)
Burst binding
Hard Case, (Edition binding)
Mechanical Binding
Saddle stitching is an economical method of binding sections collated on top of each other. Multi stitch heads on more advanced binding lines allows two sections to be stitched adjacent to each other. This can be used to bind the text and the financials, (using different paper stocks) of an annual report inside a cover.

Things to watch out for.
Adhesive binding, (Perfect), will only allow limited use before the binding will fail and pages fall out. Burst binding gives a more robust binding system.

Stitched brochures or booklets with lightweight or brittle stock can fall apart if the metal stitch pulls through the cover or inside sheet. Translucent sheets have low tear strength and easily pull out when stitched in the center or outside of a booklet.