Is destroying a paper containing Arabic words that are to be used for a tattoo considered theft, or does it fall under the category of preventing harm that could lead to ongoing sins? And should the paper be returned to the colleague with a gift and an explanation of the situation, or is this latter action considered harmful?

Tattooing is forbidden, and its perpetrator is cursed, based on the saying of the Messenger of Allah, peace and blessings be upon him: "Allah has cursed the woman who adds hair extensions and the one who has them added, and the woman who tattoos and the one who has herself tattooed." If a woman displays her tattoo in front of non-mahram men, the sin of tabarruj (displaying one's adornments) is added to that. It is not permissible to assist in tattooing through action, word, or indication, due to the Almighty's saying: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression." As for what has already occurred, if it is highly probable that she did not notice you taking the paper, then do not inform her and compensate her. If it is highly probable that she did notice, then apologize to her and explain your mistake, and make that an entry point for advising her and inviting her to Islam.