I am officially an old person, as I have subscribed to a magazine. It’s niche, but it’s been around a long time, and having enjoyed a lot of issues in my childhood that were given to me for free, I feel I should give back.
I’m wondering if there are precautions I should take. Can any sort of copy protection be put into PDFs that I should strip out? If I share them as a torrent, should I be worried that the publisher can tell where they came from?
This, essentially. Like until I tried to move music from iTunes to Foobar, I didn’t learn that metadata was even a thing, and apparently neither does Apple.
Adobe and Microsoft PDF printers retain some information. If you run it through ghostscript you'll get only the PostScript output. You can use a free utility like cutepdf to make it easy. Just install the latest gs release after installing cutepdf instead of the download they provide.