It will be about how to cut off margins (and generally resize pages) in a PDF document. For example, you need to automatically remove fields in PDF on all pages, because large margins make it difficult to read PDF on the already small screen of an e-book. The program will automatically crop each PDF page to the maximum, making the bottom, top, right and left margins to zero. If the border of the text is different on different pages, then the size of the pages will be different.
If you don't need white borders around PDF content, remove them in Adobe Acrobat XI using the Crop tool. Don't worry - you don't have to manually crop every page in a 200-page document; Acrobat offers a convenient option to automatically remove white margins from all pages at once. However, if your PDF contains scanned images, Acrobat will not be able to crop them because they do not contain pixelless margins.