Hi so basically I have some pages on my site that are the exact same page but the url is slightly different. For example when I search for an item and click on it on my e-commerce site it has a different URL, than if I found the category first then clicked on the item. Would these 2 links have a different PR despite being the same page.
No, the PR is related to the URL, and is mainly based on the number of backlinks to the given URL, so PR may be different depending on the URL! However I have a serious tip for you, as you seems to be running an ecommerce site, you need to be careful about the two link and same page. The reason is that Google Algorithm works on the basis of URL's and for Google, your same page on two URL acts like duplicate content. So you need to use rel canonical to specify the original page. I hope thats the answer to your question!
Do I still need to get a canoncial for every keyword that my item has on my site when I search for it in my site search, because that seems like a ridiculous amount of work. On amazon there product urls are sometimes different but the item is the same thing and they don't get penalized. I don't really understand it but oh well.
I believe, you are aware that, same contents in different URL are considered duplicate content in the eye of Google and are subject to penalize.
Most likely, they will have same PR nut there is possibility of being different in case both the pages have different number and quality of backlinks.