Pen plotters could accept sheets of A4 and very precisely position them since at least the 80s. I'm surprised that dot-matrix printers didn't adopt similar technologies sooner, though it could be because by the mid-80s dot-matrix printers were the budget option, fanfold paper with the tractor strips was still abundant, and it was much easier to just stick with the cheaply manufacturable technologies rather than take the risk of innovation with a product that wouldn't sell upmarket anyway.