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In addition to the links and relevance, I'd also consider if your keywords would be distinct enough from each other if you created two pages and two sets of keywords. If they are quite close to each other, then Google may get confused as to which one to rank which can lead to keyword cannibalisation issues. Generally, I'd only recommend creating two pages and allowing Google to index them if they are distinct enough from each other to avoid this problem. It sounds like this may be tricky if your new page is the same product but simply a free trial. Also remember that you could create two pages and then just stop the new one from being crawled and indexed by Google. This would prevent any ranking problems but allow you to have two pages. I'm not sure if this is worth it in your situation to be honest but I thought I'd mention it just in case. I'm sure that you could use some good design/UX and have both a free trial and a buy now link on one page - it's fairly common.