Great tip on the ownCloud, Eugene! I've got a VPS with unlimited space recently, so will definitely give it a try. Also I've just found the truecrypt app for Android (just have to wait for Lollipop update for my phone, as nothing could write directly to the card anymore): https://4sysops.com/archives/eds-truecrypt-encryption-for-android-with-dropbox-sync/

What I've done to get around the writing to sd card limitation now is keep my documents in the phone storage and then the less important stuff or static documents on the sd card. I was using dropbox but moved to owncloud last year, either one I just keep the document set I sync pretty small. Other things like the .pdf survival manual you might download I just leave on the sd card since those don't change often I don't bother to sync them.

I just kept the truecrypt volume small since OC doesn't sync chunks like Dropbox. Mine is 100M.

I've got 55Gb for free with a tablet purchase. Plan to use it. The problem with internal (nonremovable) storage is that you will loose your files if the phone dies. The T-flash most likely will survive.

Thats why I sync to owncloud, if the phone/tablet dies or is lost or stolen I have the synced copy.

Hmm, but in case of a large scale disaster the Internet/data centers might be down. On other hand, in such a situation these papers are not urgently required anyways. Is that right?

Thats why I sync and not store on the cloud.

My cloud server is my sync system so everything on each device is a copy of everything on the rest, the server simply keeps them up to date with each other.

Also since I'm running my own server I'm not dependent upon someone else and the internet, I can sync over my own network if needed or fall back on manually copying files.