I'd use Familysearch Memories. There are limitations on what you can upload (15mb per PDF or image file), but it's entire purpose is to preserve family history for as long as possible.

https://www.familysearch.org/memories/

It's a service provided by the Church of Jesus Christ of Latter Day Saints (of which I'm a member), which considers preserving family history to be a core tenet. To the point of storing family history records in the Granite Mountain Vault (https://en.wikipedia.org/wiki/Granite_Mountain_(Salt_Lake_Co...)