Your question is rather obscure because we have no context. As usual, general information is useful: OS name, LO version. I understand that your document is .pdf, but why did you tag writer?
Draw is not a PDF editor. It can marginally handle a PDF file as a collection of graphical shapes but its capabilities are rather limited and rely on stringent configuration constraints, among those the exact same fonts installed on your system as those used to create the file.
You’ll handle shapes. Whitespace does not exist in Draw. Whitespace is the empty area between shapes. Since it is empty, you can’t “delete” it. To reduce the printout, you must move individually all shapes and reposition them where you think adequate.