Well, here's what i found so far:
Do the users that want to do a purchase using their credit card information require a PayPal acount?, Is there any way to avoid this?. I'm considering to have many clients on my site thay may not have PayPal account.
Not required. You can use adaptive payments and pay as guest. Both Rest API and classic API support this payment schema. The Rest API relies on your site to handle security and PCI complience, on the second one is handled by paypal.
Does guest payment supports the Parallel payment Schema or the Chained
payment Schema?
Clasic API adaptive payments support to add multiple receivers and amounts when sendin payments, so yes, it is supported with this schema. Not sure about Rest API. The examples that I've found use just the Paypal to Paypal schema.
If I'm using the guest payment default interface (the one provided by
PayPal), should I still worry about having my site to be PCI
compliant?. I'm not storing any credit card information about the
users.
If you're using native Embedded payment flow with the dialogs and the javascript functions that paypal provides, no, it is not required. Paypal takes care of this for you. If you're using the Rest API, you have to use the payment with creditcard stored on paypal vault (however this force the buyer to have a paypal account). If you're using the Rest API to get credit card data, you have to design your site to be PCI Compliant.
I've tried to find examples about how to invoke the adaptive payment api to get the Guest payment working without any success. Does anyone know where can I find an example for this?
https://developer.paypal.com/webapps/developer/docs/classic/adaptive-payments/integration-guide/APIntro/ has Embedded flow example (however its really vague), http://paypal.github.io/ has examples for classic api implementation
Is Adaptive payment a feature of Paypal Standard?, or do I need to get the PayPal Pro subscription in order to get the Adaptive Payment Api working on my site.
Paypal pro is an account feature, not really related with the API for adaptive payments, or at least that is what I've found so far.
