The printed matter a business runs on rather than markets with. Carbonless forms, booklets, magazines, newsletters and disc packaging. Most of it is bound or multi-part, which brings its own constraints: page counts in multiples of four, and form sets that have to transfer legibly under a pen. Filter by how the piece is put together.

8.5″ × 11″ page: catalogues, manuals and reports.

Original + 2 copies. Customer, field and office each need one.

Two sheets, saddle stitched, content no longer fits four pages.

Four sheets, contents page viable, several features and real structure.

Your trim, extent and binding. Standard sizes or binding will not do.

Contents page, photo sections, a substantial quarterly or annual.

One fold, front and back: a cover, a track list and one disc.

Original + 1 copy. You and the customer, nobody else.

One folded sheet, unstitched, a single announcement or program.

One folded sheet, unstitched. A regular short update, lowest cost.

Two folds, interior spread. Credits and notes need real room.

Original + 3 copies, the job passes through four hands.

Original + 4 copies. Five parties hold the same record.

Three folds, double interior: lyrics, photography or two discs.

Two sheets, saddle stitched. It should read as an edited publication.

Your parts, size and numbering. The presets do not match your process.

Your fold plan and pockets. The fixed panel counts do not fit.

Any multiple of four, your trim. The presets do not fit the content.

Any extent, trim or binding. Presets do not suit content or postage.

5.5″ × 8.5″ page. Read in the hand, cheaper to mail.
Anything bound shares one constraint worth knowing before you plan content: the page count has to be a multiple of four, because a single folded sheet makes four pages. Asking for eighteen means paying for twenty with two blank leaves. Saddle stitching also runs out at roughly sixty-four pages, past which the spine bulges and outer pages protrude. At which point perfect binding takes over, at the cost of no longer lying flat.
Carbonless forms work on a different axis entirely. The part count is decided by how many people need an independent record at the moment the transaction happens, not by how much information there is. Be realistic about the physics too: four parts transfer cleanly with a ballpoint, five is marginal by hand, and if a form is machine printed rather than handwritten those limits do not apply at all.