Downloading Wikipedia might be helpful, and it's incredibly small compared to how large of a file you might think it would be.

Most survival instructors would probably argue that you should read books about basic survival now instead of when you are actually in a survival situation. Having the time and focus to learn survival when you are faced with it is a too much, too late.

A smartphone will also last for around 10 hours before it is completely useless. It is unlikely that you will be able to glean very much off of your documents before the battery dies. If you are anticipating an urban survival situation where a power source may be possible, I suggest posting this in /r/urbansurvivalism. A solar-powered charger may indeed be useful, but IMO, there are simply too many tasks to complete in a survival situation that would come before charging and reading your phone.

As far as micro SD cards go, I would put some encrypted copies of personal documents on there. That way, you have them if you need them and can present them to an authority source (who may very well have power and computers able to read them) without having to worry too much about size or durability. This is a really good idea and I have done the same thing.

If you are really focused on this idea, I suggest purchasing some survival books and taking notes...and then scanning those into a PDF or something like that.

Sorry if this isn't all that helpful - I subscribe to Cody Lundin's philosophy of "the more you know, the less you need." I would highly recommend that you start studying now so that you need fewer how-to guides for use if you are in an actual survival situation.