Having a quick look around it seems your not in much luck and that you need publisher to open pub files.
Not much I can suggest really as you say pageplus is out there but you'd have to start from scratch.
OnePlus 5T review: Hands-on
Illustrator Andrés Lozano on his improv line work, brazen use of colours & hand sketching
iPhone X review
Comment envoyer gratuitement des gros fichiers ?