It appears that your PDF file has a CropBox. You can enable the use of this with Magick.NET but I don't know what this will do with your other images. You will need to test that yourself. Below is the code that can be used to enable the CropBox and read a single page:
MagickReadSettings settings = new MagickReadSettings() { Density = new Density(300), // Setting this value will get you an image with a higher quality FrameIndex = 4, // Specifies the page you want to view (starts at zero) Defines = new PdfReadDefines() { UseCropBox = true// Enables the use of the CropBox. } }; using (MagickImage image = new MagickImage("3P207257-2D.pdf", settings)) { image.Write("page.png"); }