You can download all VoS forms attached to a given invoice by following these steps.
From Accounts Receivable, click on the Invoice tab
Click the checkbox next to the invoice so that the date populates on the left-hand side of the screen
Click on the blue Save button dropdown and select View
At the popup window, click on Save as PDF in the upper left-hand corner
Click on 'Include VoS forms' at the next popup window and click Download
The popup window expands. The default option is to download the invoice and any VoS forms in a zip file. If all of the VoS forms are in pdf file format, you can choose the other option to merge into a single PDF, however if any of the VoS forms are in other file formats (jpeg, docx, etc.) the system cannot merge those into a PDF document and you will want to choose the default option.