Yes, Pastela can be used for free.
To use cloud features, you'll need to sign up for the Free Plan.
Logging in with a pixiv account (linking it) automatically registers you for the Free Plan.
To access certain features, such as increased cloud storage capacity,
you'll need to subscribe to one of the Pastela Plus paid subscription plans.
To learn more about what Pastela Plus offers and its pricing, please see below.
What is Pastela Plus?