I think that the destination directory was not writeable.

#0  0x000055f6035d798d in CEditorScene::drawBackground(QPainter*, QRectF const&) ()
#1  0x000055f60360e5d9 in CNodeEditorScene::drawBackground(QPainter*, QRectF const&) ()
#2  0x00007fe2d6090776 in QGraphicsScene::render(QPainter*, QRectF const&, QRectF const&, Qt::AspectRatioMode)
    (this=<optimized out>, painter=0x7fff37dc0b68, target=<optimized out>, source=<optimized out>, aspectRatioMode=<optimized out>)
    at graphicsview/qgraphicsscene.cpp:1837
#3  0x000055f603617298 in CPDFExport::save(QString const&, CEditorScene&, QString*) const ()
#4  0x000055f6035c2eb5 in CImportExportUIController::doExport(CEditorScene&, IFileSerializer const&) ()
#5  0x000055f6035c33f9 in CImportExportUIController::exportPDF(CEditorScene&)
    ()
#6  0x000055f60356be6e in CNodeEditorUIController::exportPDF() ()
#7  0x000055f603577bc0 in QtPrivate::FunctorCall<QtPrivate::IndexesList<>, QtPrivate::List<>, void, void (CNodeEditorUIController::*)()>::call(void (CNodeEditorUIController::*)(), CNodeEditorUIController*, void**) ()
#8  0x000055f6035776e0 in void QtPrivate::FunctionPointer<void (CNodeEditorUIController::*)()>::call<QtPrivate::List<>, void>(void (CNodeEditorUIController::*)(), CNodeEditorUIController*, void**) ()
#9  0x000055f6035769b5 in QtPrivate::QSlotObject<void (CNodeEditorUIController::*)(), QtPrivate::List<>, void>::impl(int, QtPrivate::QSlotObjectBase*, QObject*,--Type <RET> for more, q to quit, c to continue without paging--c
 void**, bool*) ()
#10 0x00007fe2d50e8f4f in QtPrivate::QSlotObjectBase::call(QObject*, void**)
    (a=0x7fff37dc0f60, r=0x55f604fdf200, this=0x55f6054b35f0)
    at ../../include/QtCore/../../src/corelib/kernel/qobjectdefs_impl.h:398
#11 doActivate<false>(QObject*, int, void**)
    (sender=0x55f60544edd0, signal_index=4, argv=0x7fff37dc0f60)
    at kernel/qobject.cpp:3923
#12 0x00007fe2d50e21ef in QMetaObject::activate(QObject*, QMetaObject const*, int, void**)
    (sender=sender@entry=0x55f60544edd0, m=m@entry=0x7fe2d6277d00 <QAction::staticMetaObject>, local_signal_index=local_signal_index@entry=1, argv=argv@entry=0x7fff37dc0f60) at kernel/qobject.cpp:3983
#13 0x00007fe2d5d5c782 in QAction::triggered(bool)
    (this=this@entry=0x55f60544edd0, _t1=<optimized out>)
    at .moc/moc_qaction.cpp:376
#14 0x00007fe2d5d5f3ab in QAction::activate(QAction::ActionEvent)
    (this=0x55f60544edd0, event=<optimized out>) at kernel/qaction.cpp:1161
#15 0x00007fe2d5ee3b62 in QMenuPrivate::activateCausedStack(QVector<QPointer<QWidget> > const&, QAction*, QAction::ActionEvent, bool)
    (this=this@entry=0x55f6050848c0, causedStack=..., action=action@entry=0x55f60544edd0, action_e=action_e@entry=QAction::Trigger, self=self@entry=true)
    at widgets/qmenu.cpp:1407
#16 0x00007fe2d5eeb994 in QMenuPrivate::activateAction(QAction*, QAction::ActionEvent, bool)
    (this=0x55f6050848c0, action=0x55f60544edd0, action_e=QAction::Trigger, self=<optimized out>) at widgets/qmenu.cpp:1484
#17 0x00007fe2d5da4db8 in QWidget::event(QEvent*)
    (this=0x55f605045170, event=0x7fff37dc1540) at kernel/qwidget.cpp:9044
#18 0x00007fe2d5d62fae in QApplicationPrivate::notify_helper(QObject*, QEvent*)
    (this=this@entry=0x55f604ef00d0, receiver=receiver@entry=0x55f605045170, e=e@entry=0x7fff37dc1540) at kernel/qapplication.cpp:3640
#19 0x00007fe2d5d6b552 in QApplication::notify(QObject*, QEvent*)
    (this=<optimized out>, receiver=0x55f605045170, e=<optimized out>)
    at kernel/qapplication.cpp:3084
#20 0x00007fe2d50b16f8 in QCoreApplication::notifyInternal2(QObject*, QEvent*)
    (receiver=0x55f605045170, event=0x7fff37dc1540)
    at kernel/qcoreapplication.cpp:1064
#21 0x00007fe2d50b18ce in QCoreApplication::sendSpontaneousEvent(QObject*, QEvent*) (receiver=<optimized out>, event=<optimized out>)
    at kernel/qcoreapplication.cpp:1474
#22 0x00007fe2d5d6965e in QApplicationPrivate::sendMouseEvent(QWidget*, QMouseEvent*, QWidget*, QWidget*, QWidget**, QPointer<QWidget>&, bool, bool)
    (receiver=0x55f605045170, event=event@entry=0x7fff37dc1540, alienWidget=<optimized out>, nativeWidget=0x55f605045170, buttonDown=buttonDown@entry=0x7fe2d62a69f0 <qt_button_down>, lastMouseReceiver=..., spontaneous=true, onlyDispatchEnterLeave=false) at kernel/qapplication.cpp:2622
#23 0x00007fe2d5dbe025 in QWidgetWindow::handleMouseEvent(QMouseEvent*)
    (this=this@entry=0x55f605c5bb80, event=event@entry=0x7fff37dc17f0)
    at kernel/qwidgetwindow.cpp:580
#24 0x00007fe2d5dc0f60 in QWidgetWindow::event(QEvent*)
    (this=0x55f605c5bb80, event=0x7fff37dc17f0) at kernel/qwidgetwindow.cpp:300
#25 0x00007fe2d5d62fae in QApplicationPrivate::notify_helper(QObject*, QEvent*)
    (this=<optimized out>, receiver=0x55f605c5bb80, e=0x7fff37dc17f0)
    at kernel/qapplication.cpp:3640
#26 0x00007fe2d50b16f8 in QCoreApplication::notifyInternal2(QObject*, QEvent*)
    (receiver=0x55f605c5bb80, event=0x7fff37dc17f0)
    at kernel/qcoreapplication.cpp:1064
#27 0x00007fe2d50b18ce in QCoreApplication::sendSpontaneousEvent(QObject*, QEvent*) (receiver=<optimized out>, event=<optimized out>)
    at kernel/qcoreapplication.cpp:1474
#28 0x00007fe2d553d3ed in QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::MouseEvent*) (e=0x55f605c05ac0)
    at kernel/qguiapplication.cpp:2278
#29 0x00007fe2d5511cac in QWindowSystemInterface::sendWindowSystemEvents(QFlags<QEventLoop::ProcessEventsFlag>) (flags=flags@entry=...)
    at kernel/qwindowsysteminterface.cpp:1169
#30 0x00007fe2d18fbeca in xcbSourceDispatch(GSource*, GSourceFunc, gpointer)
    (source=<optimized out>)
    at ./src/plugins/platforms/xcb/qxcbeventdispatcher.cpp:105
#31 0x00007fe2d411e7a9 in g_main_dispatch (context=0x7fe2cc005010)
    at ../../../glib/gmain.c:3454
#32 g_main_context_dispatch (context=context@entry=0x7fe2cc005010)
    at ../../../glib/gmain.c:4172
#33 0x00007fe2d411ea38 in g_main_context_iterate
    (context=context@entry=0x7fe2cc005010, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../../../glib/gmain.c:4248
#34 0x00007fe2d411eacc in g_main_context_iteration
    (context=0x7fe2cc005010, may_block=1) at ../../../glib/gmain.c:4313
#35 0x00007fe2d5109836 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x55f605113ba0, flags=...)
    at kernel/qeventdispatcher_glib.cpp:423
#36 0x00007fe2d50b017b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=this@entry=0x7fff37dc1b20, flags=..., flags@entry=...)
    at ../../include/QtCore/../../src/corelib/global/qflags.h:69
#37 0x00007fe2d50b82d6 in QCoreApplication::exec() ()
    at ../../include/QtCore/../../src/corelib/global/qflags.h:121
#38 0x000055f60356629f in main ()