First of all, let's make it clear that blocking and pulling back are performed on your own device, and the other party will not receive any notifications directly. This means that when you block someone, they won't get a message telling you that they've been blocked. Similarly, when you add it back again, the other person won't receive a message telling you that they've re-added her.
However, while the person won't be notified directly, they may be aware of your actions in other ways. For example, when you block someone, they may no longer be able to message you or see your activity. If he or she tries to contact you but finds that he can't, he may realize that you have blocked him. Similarly, when she finds out that she can reconnect with you, she may realize that you have blocked her before.
Additionally, some social platforms may have some hint features, such as telling users that a certain contact has recently added them. If such a feature exists, then the other person may be aware of your actions through these prompts.
Of course, there is also the possibility that the other party does not know what you are doing. This usually happens when both parties don't communicate frequently or the other person doesn't pay special attention to you. If the other person doesn't pay special attention to your communication with him, then he or she may never know that you have blocked him and her and pulled him back.