Page authority (popularly known as Moz PA) is an indication of the backlink quality and relevance of a particular web page. It’s a number calculated on a logarithmic scale of 1 to 100. That means as you grow your page authority, it becomes increasingly tough to move up the ladder.
It’s important to note that a higher PA is not a guarantee to rank on the top. It’s just an indication that a page with higher PA has increased probability of ranking when compared to other web pages in the same niche but with lower PA.
Therefore, it becomes important to analyze the PA of top ranking SERP results before your start with your on-page optimization. Based on the PA of your competitors, you may need to tweak your SEO strategy to outrank them.