Often copies come back from vendors or your print department with "bates" numbers stamped electronically by the copy machine. Those pages can then be imaged, and no paper bates labels need to be affixed, one by one, at a great time savings to all.
This is good enough - most of the time. But not all copy vendors and machines have this capability, especially in the smaller office.
PDFStamper can take original PDFs and stamp sequential numbers on them, up to 2 lines of text, in fact, anyplace you wish on the page. You can also batch stamp "confidential" and other plain text or images in the same location on each eDocument.