How can I set up my template to have a transparency that goes over an image to help make the text over the image look more legible?

Here is a sample of what we are hoping to achieve:
Notice that we have the Cardinals logo, a transparent black box above the logo and text above the logo and black box.  This makes the text more readable.  Here are the steps to set this up:
1)  Create the black box image.  This image was created by following these steps:  Photoshop command: File > Save for Web & Devices as a PNG-24 with Transparency checked.

2)  Create the master pdf with a field for the Cardinals logo, a field for the black box and a field for the text on top of the black box.

3)  Create a template and uploaded the master pdf.

4)  Upload the Cardinals logo and the black box images to the graphic files area on the Assets tab of the template.

5)  In the Field Set Up tab of the template, set up the fields as follows:
Cardinals logo image field
Field type - Image from User Entry
Data Capture - select the Cardinal logo image as the default image
Format - Set the Stacking order to zero
Black Box field
Field Type - Image from Graphic File
Data Capture - Select the black box image
Format - set the Stacking Order to 3
Text Field
Field Type - Text from user entry
Format - Set the Stacking Order to 10
6) Save and commit changes
**Note - you do not need to use the exact stacking order numbers/settings.  However, the order of the fields does need to be consistent - the bottom field (Cardinals logo) should have a lower stacking order than the other two fields, and the text field should have a higher stacking order than both of the other fields.