With Wp Auto Affiliate Links Plugin you can automatically display affiliate links all over your content. You only need to specify a keyword or keyphrase to be replaced and the affiliate links. Every occurrence of that keyword will be replaced with the link. For example, Here is an example:
Add the link and keyword:
And links are now replaced.
There are many things that you can customize at the plugin, such as: the number of links to be displayed into the content, the number of same keywords to be replaced, the css class of the plugin, if links should be added only on posts, pages or homepage, etc.
You can download the plugin from the following URL: Wp Auto Affiliate Links Plugin