I bought it mostly because I have been using their PrimoPDF free export-to-pdf tool (tested a few and this one worked most consistently) - it had a few features that seemed handy and why not buy from the people who give a good free tool? (they have several single focus freeware apps=
At full price Nitro was a bit too much (i could use some features but many are lost on me) but with the rebate it was a better fit.
My main PDF needs besides just "save as" has been with °§¬|@ expense reports. Theoretically I'm supposed to scan receipts, upload them into the system, then print a summary report, sign it, scan it back and send it to india for checking... Alas I am on the road a lot on this project and finding and using printers and scanners are not what I want to waste time on. So I have been combining different tools (digital camera, photo editor, pagemanager) to avoid using a printer or scanner.
What nitroPDF adds that I didnt have with pagemanager is the ability to swap a page within the PDF if I got something wrong. What I hoped it would have that it doesn't is the pasting of a vector version of my signature - for that I still have to use Inkscape. But as Inkscape only allows single page PDF editing, the page swapping of nitro helps