I don’t know if every hiring manager does it, but when I do interviews, I take a printout of the CV and come to the interview hoping to jot down notes on the side margins of the CV. For instance, if somebody says, “I’m a team-player,” I’d ask them, “Can you tell me about a situation in which your team-playing helped in a meaningful way?” I’ll note their answer down in the margin.
Now, I’ve noticed that a lot of people struggle to shrink their entire career into 1-2 pages. So, they eat up the margins to survive. They fill up every last pixel and cram every last part of the page with text.
For one, this looks ugly. Your trick is obvious.
But more importantly, it says a little bit about your personality as well. If the recruiter/hiring manager asks you for a 1-page resume and you give them a document with no margins, it might feel like you’re skirting around the rules a little just to provide a little more information.
Think about it: You might not be that kind of person, but getting rid of the margins to include more text is a clever bending of the rules, and that doesn’t paint a particularly trustworthy picture of you.
Moreover, white space does as much work as text to make your CV readable. Maintain reasonable margins in your documents.