What does every man sign?
Rashi: If one sins, he himself signs on the day of his death that he did the sins written in front of him. Orchos Tzadikim (Sha'ar ha'Teshuvah DH ha'Shelishi) - all one's Aveiros in all his days, big and small, and all evil thoughts and idle words, and all his big and small affairs, are written in a Sefer.
Ibn Ezra #1: Some say that the rain closes people in their houses, and blocks them from going out to see what happens in their fields.
Ibn Ezra #2: Some say that Hashem signs with each person's hand the deeds that he does. This verse mentions it due to rain - "v'Hayah Im Shamo'a; ... v'Nasati Metar Artzechem."
Ibn Ezra: I say that this refers to what was planted. After rain, everyone plants. Hashem signs in everyone's hand what will result from the seeds.
Malbim: Everyone who gathered and entered in the summer will seal and close all his deeds, for then they will cease from all Melachah. Everyone signs his deeds in Sefer Zichronos.
What do we learn from "Lada'as Kol Anshei Ma'asehu"?
Rashi: To inform about what he is judged.
Malbim: After Melachah ceases, people pay wages to their workers. They calculate what each worker did, to give to him what he deserves.
