What are Affiliate Links?
An affiliate link is the hyperlink code given to members of affiliate programs. The affiliate link is displayed in webpages, emails, text ads, etc., and used to track referrals.
Do Affiliate Links Increase PageRank?
Generally no, because the majority of affiliate links point to an affiliate program script, which in turn redirects the user to the final landing page. PageRank is only passed on in direct links.
Here is an example affiliate link. If you click on it, you'll notice how it redirects you to a different website.
Here is an example of an affiliate link that points to the merchant's website. The affiliate tracking code is at the end of the link.
In recent years some affiliate programs and affiliate networks have introduced a new type of link that links directly from affiliate websites to the merchant's site.
These "bare" links meant that affiliates would link directly to the merchant's website, thereby passing on any PageRank benefits to the merchant's landing page.
This is great for affiliate program owners, but gives affiliates nothing in return. Generally I would recommend sticking with standard affiliate links, if available.