I need to do the following...

I need to have a user fill out a form with various fields, including a file uploader for a PDF. I am considering the fact that maybe I could use DocMan if the Rich Text editor loads all the same editor buttons as the core Joomla does.

Upon submission, this needs to "invoice" someone. My thought was create a table for invoicing information and the form would just add a set value to their current value in the account balance field.

Clients need to pay their invoice, but this could just be a simple paypal module where their enter the amount manually, or maybe I could do some coding to make their account balance a default for the box.

Anyways, I do not know PHP so I am very limited on this. Does anyone know if the second thing is possible, upon form submission is adds a value to the current value of a set field (account balance)?

Account balance, Paypal callback when payement is done (I think users cannot pay same balance twice, so you need to check and validate when payement is done), ...

You need to write inside your component for sure.

I moved the topic in this category to help you finding some help.
If you describe better your idea, maybe somebody can help you.

Please also precise if you search for a ready-to-paste solution, or if you just want some guidelines.