There are two methods to add an image to an existing PDF. 

Method 1 

1.  Long press on the document to bring up the quick tools menu. Tap the  button. 


2.  Options on where to get the image you would like to insert will appear at the bottom of the screen. For example, you can choose the Camera to take an image or Photos to select an image on your device. 

3.  The image is inserted into your PDF. You can resize, flatten, rotate, copy and delete the image. 

Click on the overflow icon to see more options.

Method 2

1. Tap on the toolbar switcher and switch to the Insert Toolbar.

2. Select the add image tool.