Choose the exact paper size you are printing on.
Also in the Print Dialog - Setup: choose cCntered for the Page Position.

That should do the trick.

. . .
Bert Vanderveen BNO

What Bert said.

But if you’re using a laser printer, you might not be able to get better registration. Even with Xante printers I’ve run into such bad centering that I had to stick printed sheets back to back using a light box.

Hmmm
I assume your finished size is smaller than your
paper size?
well if you can't shift the page on the printer
than you could export a pdf with crops in
indesign and replace it on a new document
(document size same as paper size)
Place the first page in the center of the page
and the second 10mm up, down, right, left.

Just to clarify I'm printing on a new HP laser machine, duplex from InDesign Booklet. There's about a 1 cm between the center lines on each side.

Sometimes, exporting to PDF and printing from acrobat gives a better result.
_____________________________________________
Personal Art and Design Portal of Ivan Gulkov
www.ivangdesign.com