You use it to help you manually fill out a new "original" return. Go to File-New. Either fill out all the info again or you can use the Forms Mode to directly enter the amounts. Then when your new return matches every line on the pdf then you can amend.
But first save the new return, File-Save As and give it a name to tell it apart like Test Original 2018 or Dup.
THEN make another copy to use to do the amended, File-Save As again and name it Amend2018.
