The Crop Pages tool is a multipurpose tool. Think of it as the change-document-dimensions tool, because it can crop as well as increase page size (Figure 12.24). While increasing the page size actually changes the dimensions of the PDF page, cropping with the Margin Controls just visually masks out the area outside the margin dimensions. Page content still exists. It just doesn’t show. That’s why cropped PDF files show no reduction in file size. Everything is still there, lurking. Since cropping isn’t final, you may find that some other applications ignore cropping instructions and show the original full content.