when I try to use 'edit copy' or Ctrl + C, libre office crashes. How can I fix?

I have LibreOffice 3.4

Which component? Writer? Calc? Draw?
What exactly are you trying todo?
Also which OS are you using?
Which version of LibreOffice are you using?

And so ancient LO … Why does someone use something so old anyway ?

Perhaps you mean OpenOffice 3.4.

What exactly are you trying to do?!

LibreOffice 3.4. I’m trying to copy and paste from a document saved as a .doc or .docx. Windows 10.

You should definately try the current version of libreOffice 5.3. That version you are using 3.4 was released back in 2011! The software has evolved considerably since, so it is possible that your problem will disappear. Try that and then come back if it doesn’t work.