Going by the limited information we have, I assume that we are talking about something along the lines of a "planned transaction" form, where there are three actions:
Primary Action 1: Authorize will actually cause the transaction to happen
Primary Action 2: Reject will prevent the transaction from happening
Secondary Action: Cancel will NOT have an effect on the transaction, but only on the user interaction (by, for example, going back to the previous screen)
It heavily depends on the context how to deal with those actions. I’m going further with more assumptions, which may not match your situation, but should give you an idea about the thought process:
I assume that the default action would be to authorize the transaction. Thus, I would …
Place the Button "Authorize" prominently, let’s say – for the sake of simplicity – left-aligned and 1/3rd of the screen wide.
"Reject" has the same level of impact, so I would place it level with the "Authorize"-Button, and of the exact same size.
To indicate the consequences I would also apply a well-learned pattern and make the "Authorize" button green and the "Reject" button red.
This leaves us with the "Cancel"-Button. Which, maybe, shouldn’t even be a button, since it doesn’t really cause an action (if my assumptions are correct!). In that case, I would place it below the two buttons, centered, as a text element.
The question is not how many buttons a form can have, but in what way multiple interactions can be presented to make their consequences as intuitive as possible.
Hope this helps at all :-)