Doc Designer Merge PDF attachment in different paper sizes

Summary:

As a sales user I need to merge construction drawings in A3 landscape paper size to the Quotation document which is in A4 portrait paper size.

Content (please ensure you mask any confidential information):

Users attach the A3 size drawing to the Transaction using a File Attachment attribute, and in Document Designer we add the attachment to the quote document using the Embedded Document > File Attachment, but only half of the added A3 drawing is shown in the generated quotation document, as is in page size A4.

If we instead use the "Attachment for Merge" function that appears when we click the print action to generate the quote, then the A3 drawing is nicely merged into one document. - But the "Attachment for Merge" popup is not shown the first time the print action is clicked. It only shows when the document has been created once (And sales users forget to select the attached drawing for merge).