Buy once instead of EndNote
2 apps in the directory cover what people use EndNote for. 1 of them is a one-time purchase, and one costs nothing at all.
Read the catch on each one before you switch — a one-time price is not automatically the better deal, and we say so where it is not.
The replacements
Zotero
free reference manager with a built-in PDF reader
Free Open source
The app is free forever, but only 300 MB of sync storage is; a PDF library outgrows that fast
Bookends
reference manager for macOS you buy once, upgrade when you like
$74.99 Paid upgrades
Updates stop after two years unless you pay $49.99 for another window; the app keeps working