1. You have no way of previewing your entered data - if you mess up, you just wasted 0.05 - 0.12 USD. Does it really cost that much to render a PDF once? With Overleaf, you get essentially unlimited previews. Consider providing a watermarked preview, or a lowly-res png render.
2. Why do the credits expire? As a casual user, I'd need to buy credits either again and again, or pay more than double the price so I can just use my credits. I think that's really unfair, and coupled with your pricing model above is limiting my interaction severely.
3. However, as a technically adept customer I like how it's done now. I can create as many free accounts as I like, each with about 7 USD worth of credits. I just need to set up a spam account every time I run out.
## Alternative model: ##
- Unlock templates by paying for them. All generation is then free (up to a certain high limit for your enterprise customers and limit abuse).
- Provide packages of templates to buy together (the finance department package, the communication package, ...) - For an even higher licensing fee, the templates can be downloaded as well and integrated into products.
I think this would suit your existing business of providing custom LaTeX templates well.
## Alternative model 2: ##
1. Bog standard subscription (pay x per month to do y pdfs)
## Security: ##
The rendered LaTeX may include files such as /etc/passwd. I did not try to get an RCE on your rendering server, but I'd spend some time isolating it as much as possible. Consider getting a pentest done, especially given your high privacy claims.