Boarder Crossing, Cruzeiro do Sul (Brasil) to Pucallpa (Peru)
 

Does anybody know if there is a road from Pucallapa to Boqueirao and if it is possible to cross the boarder there from Brasil into Peru?

doubt it. Not 4 years ago at least.
Assis Brasil to Puerto Maldonado will be your best bet. But not in the rainy season. The road is good till PM, there were it is a very small line on the map...and than where you start meeting other traffic the road gets a nightmare. Although I heard they started rebuilding in march?

Grapefruit sized rocks make it hard going after Puerto Maldonado & as you get higher its gonna be *cold*. Its a narrow road used by heavy trucks carrying timber, there are a few 'pueblitos' when you could stay but dont expect much !