How do I save a PDF file so that it opens larger?

I created a PDF document that opens too small – at about 50%. The text is too small, and I would like for it to be at 75% or 80% magnification when people open the document after I send it to them. Making the text itself larger is out of the question because it must remain on one page (it’s a resume). How do I save PDF files so that they open up larger (or more magnified?). Thanks.