Hi All,
This is one of the most frequently asked questions, I also learned the hard way, by fooling around with the mouse keys and looking closely at what then appeared in the Media Gallery display window 😉
So here's how! 😊

Just left click on the Adobe icon in the post so that the Media Gallery opens with the larger icon.
Left click on [Download], in the top left corner of the media gallery window.
Windows will then ask you if you want to Save or Open the file.
left click 'Open', your pdf reader will open it. If you have more than one pdf reader installed the Windows box may ask you 'Open With' ... your choice😉
You can then read the file and, if you want, save it to wherever you want using your PDF reader App Save command.
If you are using a 'Dumbphone / Tablet' or a different Op System - I don't know and can't help 🤔 I don't!
BTW: the site always shows 'Adobe' regardless of which PDF app you actually use.
Personally I use Nuance Power PDF as it has many more useful functions, including editing and conversion to Word doc and other formats, and no (as yet😉) security weaknesses!
Once installed Nuance also enables you to simply convert many other file types to pdf, e.g. all the usual MS Office stuff, DOC, XL* etc 😊
Cheers, Doug 😎
BTW: this also applies to any other file appearing in the Media Gallery; e.g. photos, so you can download and store them for future reference 😊
All you then need is an App on your device that can read 'em, that's your part folks 😁