Sometimes you may need to include content in your bundle from an external system such as a report that can't be produced in Calxa. Calxa does allow you to add a PDF document to your bundle, which is then merged into the generated Bundle.
Browse to Reports -> Bundles.
Select the bundle in the left navigation and click ADD A PDF.
Browse and select the PDF file to upload, enter a Name and click ADD DOCUMENT.
Drag and drop to reorder the PDF in your bundle.
Additional options such as View PDF & Replace PDF can be found in the 3 dots menu to the right of the bundle item.