When a user ask Pro license for free

ask for a video testimonial, for reviews on major sites, ask for referrals, ask for a free PRO version of THEIR stuff if relevant

Your product's $9?

I'd say no. But, you could offer a 50% discount for a good review, if that'd be useful for you.

That person probably isn't going to purchase your product at any price.

Say 'NO'. It is okay to stand your ground.

Remember, This user paid internet provider to contact you. S/He also paid computer manufacturer to contact you. S/He probably sipped a $5 specialized beverages while typing you a message.

Why do you feel need to provide this user pro license for free?

-Meera

Normally, just say no. You need to pay bills too. Your working hours also matter.

Exception: For purpose organizations or other companies that managed to exchange equivalent value

I've given an 80% discount more than once to persons who needed my app for work but struggled financially. I gifted licenses a few times too, it all depends on the circumstances described.

Generosity is cool and good, in a perfect world I'd made all my software free. Unfortunately, I need to eat and pay rent. :(

Also, I'm not losing anything if somebody who can't afford my product in the first place is getting it for free. And it's always possible to ask for a testimonial in return.

Say No.

If user think your product can solve his problem using your product then they can afford it.

ASK him to work for you one Month for free in Return

Maybe you can offer them a coupon for 1 month free, or 10% off first year instead.
I wouldn't ask for anything in return directly, but you can later (after they have used the service) ask for testimonial or review.

Quid pro quo. Nothing is truly free. They probably know this too. Get creative.