You are welcome. The safest place to store sensitive documents is under the App-folder, which is protected by Operative System and is totally inaccessible for viewing/copying on a computer. Apps with security focus tend to insist on using their own folder, or another folder protected by OS.
Even the Document, Music, Video -folder on the Phone is not a good place for sensitive documents, because thee are accessible with a computer. You can "ring, lock and delete" these, but it may be too late anyways.
I personally have all my photos on the SD card, but those are only my hobby shots, mostly nature and wildlife photos, nothing sensitive there. I have my videos, Audio and a few big Apps on the SD card too, but all of them are non-sensitive stuff.