Is there any way to password protect application folders? I have a Galaxy S4 running Android 4.2.2. When I drag an application onto another one a folder is created. I was wondering if there's any way to password protect that folder? Most of the related apps I've found so far don't do that.
There is no point in password protecting something if it is not getting encrypted, or in other words, its content not becoming obfuscated to any other program. If you simply password protect a folder using an app, then very likely you can access the folder using another file explorer or perhaps with adb too.

I would recommend encryption in this case. I use ES File Explorer which can encrypt the file. Since it encrypts the file, the file  becomes illegible to other capable file reading programs. 

You can encrypt a file/folder by long-pressing it and choosing Encrypt. Provide the password (note it down somewhere for future use) and the file will get encrypted eventually. 

If you click the file, the file explorer will ask you to provide the password. You can also opt to permanently decrypt the file by long-pressing it and choosing Decrypt.

Hope that helps!