How To Add Additional Paper Sizes To Use For Printing (Half Letter 5.5x8.5in)


I’d like to know how to add additional paper size option. I would like to use the size:
Half Letter 140x216mm 5.5x8.5in

Or the equivalent of this size in the options provided.

I checked and the paper size close to this half letter is A5 148x210mm 5.8x8.3in. I’ll try to use this and adjust margins.