PyQt Qwebengineview cannot zoom online pdf

I use qwebengineview to load web with simple code

from PyQt5.QtCore import QUrl
from PyQt5.QtWebEngineWidgets import QWebEngineView, QWebEngineSettings

class WebPreview(QWebEngineView):
    def __init__(self, parent=None):
        super(WebPreview, self).__init__(parent)
        self.settings().setAttribute(QWebEngineSettings.PluginsEnabled, True)

    def preview(self, link):
        self.load(QUrl(link))

My problem is, when loading an online pdf, such as https://www.nature.com/articles/s41524-021-00506-8.pdf the page will become extremly small when I use ctrl+wheel to zoom

However, if I load any other none-pdf web https://www.google.com/ I can zoom perfectly with ctrl+wheel

system: windows 10 python: python 3.8 pyqt5: 5.15.3 pyqt5-webengine: 5.15.3