In ghostscript-crop-pdf-not-correctly,I got a cropped PDF,but it's only seemingly cropped.The remaining content still exists in fact.
In ghostscript-removes-content-outside-the-crop-box or how-to-truly-crop-a-pdf-file or pdf-real-cropping or cropping-a-pdf-using-ghostscript-9-01 or itext-crop-out-a-part-of-pdf-file, no solution was found.May be a virtual PDF printer is the only way.
Use ghostscript or itext, Is there any way to clip a PDF file really.