Resume length is a trick subject, often with conflicting advice. Basically, a resume needs to be as tight as possible, with as much relevant information as possible and as little irrelevant information as possible. Usually, when done well, this will result in a resume that is one or two pages long. The “one page rule” is a handy guideline for some situations (like for most recent college graduates) but it is actually pretty antiquated as a hard and fast rule.
“A two page resume is fine,” as long as all the content is relevant and the two page version delivers value that a one page resume couldn’t, meaning that a one page resume would force you to get rid of accomplishments that would help you secure an interview. If we are cutting relevant material that adds value just to get to a page, then we are diminishing the value of the resume by forcing it to be a page long.
That being said, academics and people with many years of job experience can justify three, or in some cases, four page resumes or CVs. There are also different formatting issues and preferred lengths for different countries. As you can see, resume length rules vary by country, context, industry, and much more.