seeking plugin: alternate content for logged in users

i’m thinking about migrating an existing website to wordpress. i’m going to need some sort of plugin to make this work. after searching and not finding what i need, i thought i’d post here and ask for guidance.

here’s what i need:
logged in users see: a link to a pdf
non-logged in users see: a link to buy a pdf

(the site has a subscription model, monthly subscribers get all the pdfs they want, non-subscribers can buy pdfs a-la-cart.)

i did find some php code in the forum that looks like it would work here: https://www.ads-software.com/support/topic/121151

…but i’m hoping there might be some sort of plugin to manage all the pdf links instead of having to put php into each post. maybe i need to become a plugin author, it probably wouldn’t be too hard, right? but i’d rather not re-invent the wheel if someone already wrote something suitable.

many thanks in advance for any help!