Dropbox DocSend - Dropbox DocSend is a secure file and document sharing solution that gives users analytics and control of document in their critical workflows. Key features include sending documents as secure links, eSignature, and customizable virtual data rooms.

PDFTK Builder - PDFTK Builder is a free graphical interface to for PDFTK, making it much easier to use.

Attach - Gain the insight and control you need to close more deals. Attach helps you understand how your customers interact with your content so you know how to time and tailor your follow up for maximum impact.

QPDF - QPDF is a command-line program that does structural, content-preserving transformations on PDF...

Locklizard Safeguard PDF Security - Locklizard Safeguard PDF Security provides total PDF DRM protection and control over your documents...

PyPDF2 - PyPDF2 - A utility to read and write pdfs with Python