The below code behaves same and works as expected :) :)
It saved lot of time to me :) :)
MagickReadSettings settings = new MagickReadSettings()
{
Density = new MagickGeometry(300, 300)
};
newSettings.SetDefine(MagickFormat.Pdf, "use-cropbox", "true");
newSettings.SetDefine(MagickFormat.Pdf, "use-trimbox", "false");
Thank you once again for the helpIt saved lot of time to me :) :)