Our PDF Stamper creates a new PDF for each buyer with security settings that may differ from the original in a predictable way.
Because of the way our Stamper works as a PDF authoring program itself and creates a brand-new PDF document for each buyer, it has to re-apply any security settings itself; these cannot be simply duplicated or "carried over" from the original source document on a case-by-case basis. Thus, the Stamper applies sensible editing restrictions that prevent actions relevant to piracy/plagiarism or removal of the stamp, while allowing other actions that many PDF sellers may actually want buyers to be able to perform.
Our PDF stamper does add an extremely long, random author/edit password to each buyer's copy, which forbids document creation (adding/deleting/changing the existing content) and document assembly (adding/removing/reordering pages), which are the only editing capabilities relevant to piracy or plagiarism. Restrictions on printing or copy/paste actions can also be added to the stamped files by using the &pdf_allow_copy=n&pdf_allow_print=n parameters in our PDF stamping URL.
However, the Stamper also permits superficial editing actions which do not affect the original content, such as filling in form fields, adding comments, and adding a digital signature key. For instance, a buyer might be expected to type some data into some form fields provided in the file, add a digital signature key to prove it was really them who filled in the form, and then submit the completed file somewhere.
