"As many pages as is needed to tell your story."
Your resume should be as long as it needs to be to illustrate your abilities and achievements. I got hired with a four page resume. I've seen resume's as long as six pages.
There is no hard,fast and specific rules about resume lengths. Certainly about font size though. Never go smaller than 10 pts. If it needs to be longer, don't try to force it into a set number of pages. If it is forced, it will look forced and that counts more against you than going one more page to comfortably fit things in.
The most important thing about a resume is that it piques interest.
The point of the resume is not to get the job, it is to get the interview.
A few general rules of thumb:
- Avoid gimmicks and trends, the most interesting thing about your
resume should be the content, not the format.
- Use "action" words
- Avoid repetition
- Summarize, don't explain
- include industry jargon, most resumes never get seen by anyone unless they can pass a keyword filter.