Challenge: Make people pay for something they've got

Hi,

I have an interesting challenge. How do you get people to voluntary pay for something they've already downloaded (like an eBook)?

Here's the scenario:
I've got a website which let's users

a) upload a document (docx)
b) server converts document to another format (doc)
c) users are given immediate download link to converted file

Now, my main goal is to get happy users (because happy users tell their friends) and provide a fast and convenient conversion service online. But - I need money to pay for the bandwidth costs. So, how do I get more people to voluntarily pay after they've downloaded their document?

My point is: the conversion is NOT free, but at the moment less than 0.5% of my users are honoust enough to pay the small price of $2 USD

Please see the following to screenshots:

Step 1


Step 2


...do you have any advice with regards to the wording or process - how do you get more people to pay for something they've already got? It's like giving a kid candy - and ask for money when he has already ate it.


I can easily make the site pay-first-download-later, but I want to provide good service to my users.

In Norway we have quite a few un-staffed toll roads in the mountains. It's all based on trust - drivers pay the road toll voluntarily....

 

Surely someone could do this manually themselves?
What does the website do that's "special"?

 

Don't know I didn't really understand why would someone not press save as and save it to a different kind of file... then someone pays 2 dollars for the conversion.