An ODT file text document was set to A4 paper size (21.0 x 29.7cm, 8.27 x 11.69 inches), but exporting (File → Export as PDF) as PDF, LibreOffice creates incorrect PDF paper size - 8.26 x 11.69 inches! Correct PDF A4 size must be 8.27 x 11.69 inches. I think it’s a software bug.
Libre Version: 5.2.3.3