Took me some time sorting through the extensions in the same category to find this.. An excellent extension, I wanted to choose where to insert Ads in my content, and this extension lets you specifically choose how many paragraphs up or down in the main content for your ad to appear. Then I got thinking and decided I wanted to specify two ad positions in the main content, one so many paragraphs up from the bottom and another so many paragraphs down which the extension at this time cannot do. A quick message to the developer on his forum and he promised to include this in the next version! (I see in the forum he's promised additions before and has delivered).
I can recommend this if you want more flexibility than just the set positions that other extensions in the category offer.