Edit and Optimise Current Web Pages For SEO Purposes

Hello, We have a web design agency and we are looking to improve a number of pre-exisiting pages for SEO purposes. To do this, we are looking to rewrite parts of particular web pages, adding additional keywords, while ensuring the content is written for the end-user and not spammy.

We use the tool Surfer SEO, this will provide guidance on what terms we wish to include and the number of times the term should be used.

Initially I would like to concentrate on two pages first, then we can improve more pages of the website.