DOCX save as PDF with transparent PNG (black background)

Hello!
Can you please tell me how to get around the problem with saving DOCX in PDF, which has a drawing in PGN format with a transparent background. As a result of saving, the entire transparent background is replaced with black. Can you somehow solve this problem? Maybe someone came across. Thank you.

Ops. Sorry. The problem has been resolved. I used PDF/A1 format. Transparency is prohibited in it.