File Permission problem still not solved.

I have opened two threads about this problem. Both without a clear resolution.
I would like to know how to confidently get around this problem. Can someone assist please?

http://forum.librecad.org/Correct-prodedure-for-avoiding-file-permission-problem-td5714520.html

http://forum.librecad.org/Correct-prodedure-for-avoiding-file-permission-problem-td5714520.html#a57

  What operating system are you using. Linux, winders, or Apple?

I am using Linux Mint 17.3

 Mate or cinnamon?  
 I am using mate 17.1.
 I open a terminal in directory and type in:

chmod 777 my_locked_file

  Or:

chmod 777 lmy_locked_dirctory

Keghn,

I am using the KDE desktop.
Are the instructions you listed above a method to recover "lost" files?