An advertiser wants to improve their position without necessarily increasing their bid. Which action would most directly impact their rank?

The most direct action is refining the quality and relevance of the ad and landing page. Ad Rank is not decided by bid alone: it combines the bid with ad and landing page quality, the Ad Rank thresholds, auction competitiveness, the context of the search, and the expected impact of assets and formats. Quality is the lever an advertiser can pull without spending more per click. Writing ads that answer the query directly, making sure the landing page delivers what the ad promised, and improving page speed and usability all raise expected click-through rate, ad relevance and landing page experience. A higher-quality ad can outrank a higher bid, and it usually costs less per click as well, because Ad Rank influences what the advertiser actually pays. That is why quality work is the first response to a position problem, before any bid change.