My grandfather died with no will. My uncles want everything transferred to my grandmother. Their lawyer sent a document for my mother to sign, waiving her inheritance and authorizing court representation (non muslim country). If I print it for her to sign, am I helping with something haram or kufr?

Ustadh AbdulAziz al-Haqqan

You suffer from waswas and you should work on that. As for depriving her of her inheritance, this is not allowed and they should fear Allah. Where will they run from Allah if they take her right that Allah has legislated for her?