The MongoDB Driver does provide a method for deserializing from Bson to your type. The BsonSerializer can be found in MongoDB.Bson.dll, in the MongoDB.Bson.Serializationnamespace.
You can use the BsonSerializer.Deserialize<T>() method.
Some example code would be
var obj = new MyClass {
MyVersion = new Version(1,0,0,0)
};
var bsonObject = obj.ToBsonDocument();
var myObj = BsonSerializer.Deserialize<MyClass>(bsonObject);
Console.WriteLine(myObj);
Where MyClass is defined as
public class MyClass {
public Version MyVersion {get; set;}
}.