You can add a stamp to your Digital product in the following steps:
1. First you need to define the stamping template.
2. Go to Settings and click on the Stamping tab.
3. Click on the Add Stamping template button and configure your template as shown in the video below.
4. Go to the Commerce tab and click Products. Select the digital product you want to add a stamp.
5. Go to Downloadable content and attach your pdf file.
6. Click the stamp editor icon by the file and select the template you want.
7. Publish your product.
8. PDF Stamping is available for Memberships, Courses, Forms, Funnels and Degrees.