They are PDFs, right? They own the copyright of the PDFs of those publications, because they made the PDFs. Just like a Penguin edition of a public domain novel is copyrighted for that edition. Microfilm/microfiche works the same way. Same with images of old paintings in museums--the painting itself is in the public domain, but the copyright of photographs of the paintings belongs to the photographer.
So you can go ahead and make copies of the same magazines that you bought off eBay and sell them, yes. YOU would own copyright of THOSE editions.