[Calvin Locke]

I was PO'd at first, when MS made Edge the default for PDFs last month.

FF and Brave are fast viewers. My own preference is to avoid Adobe, and that alternative viewer - can't even remember the name - became too annoying to tolerate any more.

Libre Office and the one with Calibre can be too slow.

[Bikkuri]

You should try Foxit (PDF Reader).

I have been using it for years as a replacement for Adobe reader... it is fast and not resource heavy.

https://www.foxitsoftware.com/