Comment by roryirvine

Sizing errors are essentially unheard of, and I've never seen anyone having any trouble with joining or folding ISO paper to go one size up/down. It's a completely normal operation, which people working in printing and publishing will routinely do without a second thought.

For commercial printing, there's the SRA paper series (Supplementary Raw) which is designed to accommodate bleed and alignment bars. An A4 glossy magazine, for example, might be printed on SRA3 and will be trimmed, folded, and stapled automatically at the end of the printing process. But that's a technical detail for the printer to care about - the publisher or designer might specify "folded A3 with bleeds", and the printer will choose the correct raw format to provide that within their printing system.