[Enhancement]: Allow PDF download of pending invoice

### Affected Area

None

### Problem Statement

The user would like to download the pending invoice so they can attach it to a file and obtain approval for the required funds.

### Proposed Solution

The user should get an option to download the pending invoice.

Start by locating the pending-invoice view and the existing invoice generation or download flow in the Press repository. Trace how a pending invoice is displayed and identify the relevant approval-related behavior shown in the issue. Done means users can download a pending invoice for attachment and approval, with the existing invoice behavior still working.

Written by the indexing model from the issue text.