the object you wish to serialize should be marked serializable or should
implement ISerializable interface
more on that at
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cp
conserializationguidelines.asp

The PrintDocument class contains a method called CreateObjRef which is used
to create a proxy for communication with a remote object
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlr
fsystemmarshalbyrefobjectclasscreateobjreftopic.asp

I don't think that would be a good idea. Isn't a PrintDocument object
printer dependant? Also, it would be very large. I think it would be better
to send a class that has enough data to render the PrintDocument.