This is easy with Notepad++ as I’ve done the same with plays.
Load the file in Notepad++ and press “Alt-Shift +C” or View->Show Symbols->Show all characters
That will show you line breaks. They’ll look something like this.
CHARACTER A: blah blah blah CRLF
This may vary depending on your system. I believe Windows uses CRLF as a line break.
A simple fix would be to replace all CRLF with two CRLF. This is done in Search-Replace.
NB: Make sure Search Mode is in “Extended” mode first!!
CR(Carriage Return) is represented with a \r
LF(Line Feed) is represented with a \n
Then search for “\r\n” and replace with “\r\n\r\n”. This works well enough for me. You will need to experiment here depending on how your document was formatted.