This is the 524th most frequent Arabic word.
عليهم
"Upon them" or "on them."
In this sentence, 'عليكم' (a variant of 'عليهم' for addressing the second person plural) denotes obligation or responsibility directed to the addressed group.
قال المعلم لطلابه: يجب عليكم التركيز على الصف.
The teacher said to his students: You must focus on the class.
Here, 'عليهم' indicates the target group of a supplication or invocation.
دعا عليهم بالخير والرزق الوفير.
He prayed for them to have goodness and plentiful sustenance.
In this case, 'عليهم' refers to the surfaces of the papers on which something was written.