Kami is an app that you can add to Chrome as an extension.  

It will allow you to add content to PDFs.

Link to install - https://goo.gl/fVZKdF

Installing/Using Kami on a Chromebook - Video Link

Submitting Assignments with Kami into Buzz - Video Link

Once you click the link, you will see the following screen below, you will want to click on Add to Chrome.

You will then get the prompt to Add App, click the button to install the extension on Chrome

Once the installation is finished, you will see the Added to Chrome button on the top of the screen

The following window will also pop up after installation asking if you want to login with Google Drive, or you can Skip this Step

When selecting Skip this Step, You will see the following options.

You can click on the Folder icon in the top right corner to open files or use the icons in the center of the screen.

See the following tutorial below if you need help navigating Kami or want more information on its use

Using Kami to Edit PDFs