Help with printing in a specific manner

Hey everyone,

Sorry if this is really simple, but I never had to try it and seem a bit lost....
I have a PDF file, with 6 pages. Those were supposed to printed in standard A4 sheets, one page per sheet.
But I need to print it 3 pages in a sheet in landscape orientation (first to a PDF file and later to real paper). However, the only options I see only allow to pick 2 pages per sheet or 4 pages per sheet.
How can I do this? I have tried deleting the last 3 pages, so there would be only 3 pages available for printing, but the result was that there was a left white space in the sheet.

Any help is greatly appreciated! Thanks!