Download reCAPTCHA filter: Actually acts as a captcha filter to pdf downloads. It intends to be a very CMS agnostic tool.
Includes reCAPTCHA php library (recaptchalib.php from http://code.google.com/p/recaptcha/downloads/list?q=label:phplib-Latest).
Known issues:
- If isn't passed the reCAPTCHA right-click "save as..." doesn't run.