Even if you are only sending in copies digitally, it is a good idea to print your resume (as it’s possible that hiring managers may be doing so) to be sure it prints on a single page, and is easy to read in printed form. Reading over a printed copy of your resume will also help you ensure that there is plenty of white space on the page and it looks professional.
One of the biggest mistakes you can make when applying to jobs is sending the same generic resume out for each one. Sure, you can apply to more jobs if you don’t take the time to personalize your resume each time, but chances are you won’t get interviews from any of them. If you take the time to tailor your resume, even though you’ll be applying for fewer jobs, you’ll get more interviews.