If I met a person yesterday, could I say, now, "I am glad to have met you" ?
Or is it better to say: It's been a pleasure to meet you?
"I'm glad to have met you" sounds better. It's equivalent to saying "I'm glad to have known you."
I'd say "It's been a pleasure to meet you" just before saying goodbye to someone (e.g. at the end of a business meeeting).
If you met them yesterday, and you're talking with them today — and you actually want to express that you are glad to have met them, rather than just express a friendly and polite formality — you should say "I'm glad [that] we met [yesterday]". This is especially true if you want to say it when you are not parting from one another, and you wish to continue by explaining some reason why your meeting was timely or fortunate
I think the better one is..
"It's been a pleasure to meet you"
'I am glad to have met you' is far too formal and one would only say it if the person in question has had a considerable impact on him/her or helped him/her in some way