Issuu is a famous digital publishing platform for Magazines, Catalogs, and more which count millions of readers.
The publishers can decide if the publications can be downloaded or not.
If you haven’t this option you can use some services that allows anyone to download the publications so you can read offline.
It’s very simple, you just need to paste the publications URLs and automatically the PDF will be generated and will be ready for the download.
Within Pasty.link service will be generated jpeg images for each page.