diff --git a/sources/cli_export.cpp b/sources/cli_export.cpp
index a132a8e29..aa6c96052 100644
--- a/sources/cli_export.cpp
+++ b/sources/cli_export.cpp
@@ -227,6 +227,7 @@ int exportPdf(QETProject &project, const QString &output,
 	// Rewrite the URI link annotations into native internal GoTo actions, so
 	// the cross-references jump inside the document in any PDF viewer.
 	PdfLinks::convertUriToGoTo(output);
+	PdfLinks::removeUnusedPdfxNamespace(output);
 
 	out << "Exported " << diagrams.size() << " page(s) -> " << output << "\n";
 	return 0;
diff --git a/sources/pdf_links.cpp b/sources/pdf_links.cpp
index 5458f396b..6bdf563c1 100644
--- a/sources/pdf_links.cpp
+++ b/sources/pdf_links.cpp
@@ -388,6 +388,29 @@ void convertUriToGoTo(const QString &pdfPath)
 	out.close();
 }
 
+void removeUnusedPdfxNamespace(const QString &pdfPath)
+{
+	QFile f(pdfPath);
+	if (!f.open(QIODevice::ReadOnly)) return;
+	QByteArray data = f.readAll();
+	f.close();
+
+	// Qt only fills the pdfxid namespace in when it writes PDF/X-4.
+	if (data.contains("pdfxid:GTS_PDFXVersion")) return;
+
+	static const QByteArray decl =
+		" xmlns:pdfxid=\"http://www.npes.org/pdfx/ns/id/\"";
+	const int pos = data.indexOf(decl);
+	if (pos == -1) return;
+
+	// Same length, so the stream /Length and the xref offsets stay valid.
+	data.replace(pos, decl.size(), QByteArray(decl.size(), ' '));
+
+	if (!f.open(QIODevice::WriteOnly | QIODevice::Truncate)) return;
+	f.write(data);
+	f.close();
+}
+
 void convertComponentInfoAnnotations(const QString &pdfPath,
 									const QList<ComponentInfo> &annotations)
 {
diff --git a/sources/pdf_links.h b/sources/pdf_links.h
index 27e266420..325367c53 100644
--- a/sources/pdf_links.h
+++ b/sources/pdf_links.h
@@ -74,6 +74,15 @@ namespace PdfLinks {
 	*/
 	void convertUriToGoTo(const QString &pdfPath);
 
+	/**
+		Post-process a Qt-generated PDF file: blank out the PDF/X namespace
+		declaration Qt 6 writes into the XMP metadata of every PDF.  Adobe
+		Acrobat draws small text too bold when it is present (bugtracker #340).
+		Replaced in place with spaces, so no offset changes.  No-op for a real
+		PDF/X file or when the declaration is absent.
+	*/
+	void removeUnusedPdfxNamespace(const QString &pdfPath);
+
 	struct ComponentInfo {
 		QString contents;
 	};
diff --git a/sources/print/projectprintwindow.cpp b/sources/print/projectprintwindow.cpp
index e6b86efa5..3204a8527 100644
--- a/sources/print/projectprintwindow.cpp
+++ b/sources/print/projectprintwindow.cpp
@@ -874,6 +874,7 @@ void ProjectPrintWindow::print()
 			// Convert URI link annotations into native internal GoTo/FitR
 			// actions so cross-references jump inside the document.
 			PdfLinks::convertUriToGoTo(pdfFile);
+			PdfLinks::removeUnusedPdfxNamespace(pdfFile);
 
 			this->close();
 		});