Your resume is a brief snapshot of your most relevant background history, focusing attention on your specific experience and skills that match a particular job. This is your marketing tool and only needs to include enough information to prove that your experience matches the job description - without overwhelming the recruiter. In most cases this document does not need to show more than 10-15 years of prior experience, along with education, skills, a brief career summary or career highlights. It is best to avoid adding every small detail of every prior job.
There are many opinions about how many pages one’s resume should be, and there is actually no simple answer. The number of pages really depends on your experience, your field of work and the job to which you are applying.
For a long time it was thought that a resume should only be one page; however, that thinking has changed. The rule of thumb is for individuals with under 10 years of experience, recent graduates and entry-level candidates, one page should suffice to present your qualifications and experience. For the more experienced candidates, recruiters are looking for specific skills, background, and career progression; therefore two pages will provide a better opportunity to reveal your accomplishments within various jobs. For highly specialized, experienced candidates, an additional page may be necessary - especially if there are technical requirements. A three + page resume would typically be best for senior level executives; scientists; government professionals; and technical project managers, which may include Case Studies, Transactions or Project Highlights.
More important than the length is the presentation of the information and keyword optimization. The goal is to present your information so that the ATS scan will pass your resume on to a recruiter. So the resume should include skills and terms that support the requirements of the job of interest directly from the job description - whenever possible.
Readability is also important. If you add too much language into too little space, with lengthy sentences and phrases, the recruiter will have a difficult time reading it. Using a proper Font size, 11-12, including spaces between topics, and adding bullets, will make the document easier to read and follow. The idea is to present the salient information that maximizes your viability as a candidate in as few words and pages as possible.
If you are writing your resume for the first time, start by writing all the information you think you need to share in a first draft. Compare your information to the job description, and check for keywords. Then proofread and edit. Edit again! Minimize language. Once you have achieved your perfect resume, whether it is one page, or more, it will likely be acceptable to the hiring manager.