Generate or update a PDF to include an encrypted, hidden watermark?
- by Dave Jarvis
Background
Using LaTeX to write a book. When a user purchases the book, the PDF will be generated automatically.
Problem
The PDF should have a watermark that includes the person's name and contact information.
Question
What software meets the following criteria:
Applies encrypted, invisible watermarks to a PDF
Open Source
Platform independent (Linux, Windows)
Fast (marks a 200 page PDF in under 1 second)
Batch processing (exclusively command-line driven)
Collusion-attack resistant
Non-fragile (e.g., PDF - EPS - PDF still contains the watermark)
Well documented (shows example usages)
Ideas & Resources
Some thoughts and findings:
Natural language processing (NLP) watermarks.
Apply steganography on a randomly selected image.
http://openstego.sourceforge.net/cmdline.html
The problem with NLP is that grammatical errors can be introduced. The problem with steganography is that the images are sourced from an image cache, and so recreating that cache with watermarked images will impart a delay when generating the PDF (I could just delete one image from the cache, but that's not an elegant solution).
Thank you!
