16K paper size is 185*260mm, and A4 paper size is 2 10*297mm. So 16K paper is different from A4 paper, and 16K paper is 16 paper.
The size of 16K paper has been listed above. Just select 16k from the paper options drop-down menu on the paper tab in word page setup. The key is that the printer you are connected to must support 16K printing paper to print smoothly. Printers in general print shops support 16K paper printing. The general multifunction machine can basically support the printing of 16K printing paper.
I hope I can help you solve the problem.