You don't have to make an explicit pact, but the Grim Verum suggests, in spirt work, you're always making a pact, even you intend to or not. So you might was well take it seriously. Half-assing something never gets anyone very far. In the GV protocols it's meant to be the beginning of a deep journey and friendship. There are benefits to this approach I leave for people to discover.
Just to help put to rest some of Hollywood horror movie fears, a excellent introduction to the pact-based grims, from Secrets of Solomon, edited by Joseph Peterson, an early proto-GV:
“The spirits are certain hidden forces, who will not willingly serve unless you make an alliance and unite with the strength of an agreement (or pact), by means of a certain specific character from Sigambach, or his secretary Rabidmadar with the intention spelled out. Nevertheless this character is nothing else but an emblem, in order that friends can be distinguished from enemies; so great indeed are they, that the spirits will not aid you unless they can distinguish and discern by some sign, that it is one of his friends calling for help. Moreover, they will not aid unless you have shown some kind of conspicuous declaration beforehand, such as an agreement or pact that was entered into between you and itself - clearly indicating you as his friend, and you should show a suitable offering. Understand, a trusted friend is one whom the spirit himself has willingly accepted mastery.”
Another paragraph in the GV tell us how to work with the spirits:
”The spirits, who are powerful and exalted, serve only their confidants and intimate friends, or if a pact has been entered into, or their service can be acquired by means of certain characters at the will of Singambuth, or his secretary.”
This is more about friendship than formal alliances than "selling your soul" - if anything you are offering to make available , as a freind, your time and attention. (and a little bit of access to your Logos-insipired divine creativity. ) I will add here the pact is two-way street. As much as you can summon them, they can summon you as well.