addScript problem (can't add a script to multiple documents via Batch)

Hello all. I'm commonly on this forum researching problems, but have never posted before. Hopefully you can help me as you've helped many others.
 
I've been manually adding a javascript to PDF's. All the javascript does is to open a pop-up window with a message whenever a PDF is opened. I've been adding the script by going to Advanced > Document Processing > Document Javascripts > Add, then I paste in this bit of code:
 
var UsageAgreement = "This text is what shows up in the pop-up window"
 
app.alert(UsageAgreement,3);
     
Since I have to do this literally hundreds of times I'm trying to make a batch which will insert this code into every PDF at once. I'm very close, but can't get it to work. I was told to use this code:
 
this.addScript("Script name goes here", 'Script goes here');
   
But when I change the "Script name goes here" to my script name, and replace "Script goes here" with my script, like this:
 
this.addScript("UsageAgreement", 'var UsageAgreement = "This text is what shows up in the pop-up window"
 
app.alert(UsageAgreement,3);');
 
It doesn't work and gives me an "unterminated string literal" error. If I remove the "var UsageAgreement" and "app.alert" parts, it will correctly insert the "This text is what shows up in the pop-up window" into the javascript field of every document, but the pop-up window won't work without those commands.
 
Any help would be appreciated.