It's important to only download magazines from legal sources to avoid any legal issues.
As mentioned before, downloading copyrighted material without permission is illegal. However, here are some websites that offer free magazine PDF downloads of public domain and open-source content: Free Magazine PDF Download

Project Gutenberg - Project Gutenberg is a digital library that offers over 60,000 free eBooks. You can download magazines from their collection of public domain content, which includes classic literature, history, and more.
Open Library - Open Library is an online digital library that offers free access to over 1.7 million books and periodicals. You can browse and download magazines from their collection, which includes public domain and open-source content.
ManyBooks - ManyBooks is a digital library that offers free eBooks and magazines. You can browse their collection of public domain and open-source content, which includes classic literature, history, and more.
It's important to be cautious when downloading from any website, and to ensure that the material being downloaded is in the public domain or has been made available through open-source licensing.