I don't want to go into the whole tabs vs. spaces argument here, but you mentioned cleaning up the document, and you've made it look worse on my end. Phoenix's wasn't perfect, but the text is even more off now. While you can use Notepad++ to replace tabs with spaces, it's just not going to give decent results in this document. What you can do is use its option to insert spaces instead of tabs:
Settings -> Preferences -> Language Menu/Tab Settings
Tab Size: 8 (or whatever)
Replace tabs by space.
When you hit the tab key, it'll insert the correct number of spaces, working exactly like a normal tab (unlike the replace option, which always inserts X spaces, rather than up to X). It'll take a little work converting manually, but it'll be worth it for ensuring the document looks the same to everyone. Unfortunately, the replace option can't automate this for some reason (you'd think if you told it to replace all tabs with tabs when you had this setting enabled, it would do spaces instead, but it doesn't.)