How to lock either documents and/or folders in OS X?

[DigitalAR]

I saw a folder that I wouldn't want anyone to ever see. That folder contains 2 documents; one Pages and one PDF file.

Am wondering how to most easily go about making sure these documents and folder won't be visible to anyone.

I do have password required to log into my iMac, but wanna take an extra step just in case anyone ever comes across this folder that resides on both my OS X desktop and also an exact duplicate exists on my (always connected) external SSD drive.

Is there an app that can do this for me for ease?

 

[chown33]

You can convert the folder into an encrypted disk image. I think there's a one-step action, either menu-item or toolbar icon, that can do this in Disk Utility. Otherwise it's two steps:
1) Make an empty encrypted disk-image (Disk Utility)
2) Move the files to the disk-image (Finder)