when I make pdf of any drawing... the pdf size become double of dwg size .. for example my dwg size is 3mb.. but when I make pdf it will became 6mb or langer then 6mb.... please help why this happened?...

What method is being used to create the PDF?  This article may be of some use.Autodesk/AutoCAD/Revit and PDF creation – Bullzip Knowledge Base

ok I will try this... I used control+p comand, than select dwg to pdf and than after selecting paper size I plot the drawing into pdf ... I will try that what you have suggested to me and will return back to you. thanks alot...