How to change page size of pagelayout ?

Hi,

I have a A3 printer (size: 297mm x 420mm). But I am wanting to print my pagelayout with paper size is: 265mm x 380mm

I tried to change the page size of my pagelayout to 265mm x 380mm by using the statement:

And, I tried to setup printer properties to A3 size or custom size (265mm x 380mm) but it is not successfull (it shows incorrect position).

Do you know how to fix it ?

Thanks and regards,

Tai