Given the quantity of free PDF editing tools available online (including the native tools present within a PDF file), it isn’t all that difficult to make small-scale changes to PDF documents when the need arises. Making those same changes at a greater scale, however, presents an entirely new challenge.  

Let’s say you have 100 PDF files, each requiring the same editing operations.  In this case, it doesn’t make sense to perform the changes manually: the inefficiency of that process ultimately creates more problems than it solves, getting in the way of competing tasks/priorities.  The most efficient way to make changes to large volumes of PDF documents at scale is to do so programmatically, using APIs which are designed to communicate with compressed PDF files and manipulate their properties with ease.