At Yoast, we practice what we call ‘holistic SEO‘. This means that your primary goal should be to build and maintain the best possible website. Don’t try to fool Google, but use a sustainable long-term strategy. Ranking will come automatically if your website is of extremely high quality. Google wants to get its users to the right place, as its mission is to index all the world’s online information and make it universally accessible and useful.
If you have original, quality content on a site, you also have a chance of generating inbound quality links (IBL). If your content is found on other websites, you will find it hard to get links, and it probably will not rank very well as Google favours diversity in its results. If you have original content of sufficient quality on your site, you can then let authority websites – those with online business authority – know about it, and they might link to you – this is called a quality backlink.
The audit is for all pages and not only one. What happens in the majority of the cases is that pages / posts have similarities so you can group them together. For example the pages of a website may be ok but the blog post pages may be missing titles. It’s a lot of work especially for a 500 pages website but you can start from the most important pages first and work your way to the rest