added PDF/A-1b compliancy to all PDF export functions

for more details about this look at: https://www.kdab.com/creating-pdfa-documents-qt/

src/Mod/Spreadsheet/Gui/SpreadsheetView.cpp

@@ -255,6 +255,8 @@ void SheetView::printPdf()
         QString::fromLatin1("%1 (*.pdf)").arg(tr("PDF file")));
     if (!filename.isEmpty()) {
         QPrinter printer(QPrinter::ScreenResolution);
+        // setPdfVersion sets the printied PDF Version to comply with PDF/A-1b, more details under: https://www.kdab.com/creating-pdfa-documents-qt/
+        printer.setPdfVersion(QPagedPaintDevice::PdfVersion_A1b);
         printer.setPageOrientation(QPageLayout::Landscape);
         printer.setOutputFormat(QPrinter::PdfFormat);
         printer.setOutputFileName(filename);