How to modify BSON in C#?

My server gets data from MongoDB as BsonDocuments (not strongly-typed as POCOs). Before sending that data onward to the client, the server must change a number of things. JSON.NET has a good API for doing this, with methods like JContainer.Descendants, JObject.Properties, JToken.Replace, etc. But I’m wondering if I can avoid the extra step of converting the BsonDocuments to JObjects. Does the MongoDB C# driver have a good API for doing this sort of thing directly on BsonDocuments?