Download and install 3D PDF Exporter for Revit.

Run Revit and load a model.

There is a new toolbar panel named '3D PDF Exporter'. 

It contains three ribbon buttons as mentioned below.
A) Export
       1. After clicking Export, a “Secure PDF” dialog will display on your screen(Refer to Screenshots).
           You can encrypt and secure your PDF document by assigning a password to it.
           This is a user password and will be needed to open the document.
           After selecting the “Require a password to open a document” check box, password fields will be enabled where you can enter your password.
           If you tick that check box off, password fields will be disabled and no password will be assigned to the pdf.
           If you do not wish to pop this dialog every time, you can tick the checkbox “Do not show this dialog again”.
           You can revert this setting from preferences.
       2. After you press OK, a 'Save As' dialog will display on our screen. Click the Save button to export the current model to a PDF file. 

B) Preferences
      It contains a set of features in which you can control the different parameters to get the desired output. 

C) About
      It displays information about the product. It provides the facility to activate your product license at any time.

D) Merge PDF

      1. After selecting the Merge option, a 'Save As' dialog box will display on your screen.

      2. Click on the Save button to merge the selected PDF. 

NOTE:

1. For the PDF Password and Template feature, use Abode Reader.
2. Please ensure that you must save the project before export.

Install:
The installer that ran when you downloaded this app/plug-in from Autodesk App Store, will start installing the app/plug-in.
                                                             OR
Simply double-click the downloaded installer to install the app/plugin. You may need to restart the Autodesk product to activate the app/plug-in.

Uninstall:
To uninstall this plug-in, exit the Autodesk product if you are currently running it. Simply rerun the installer and select the "Uninstall" button.
                                                                              OR 
You can uninstall it from 'Control Panel/Programs and Features' (Windows 7/8.1/10/11), just as you would uninstall any other application from your system.