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!