myPDFViewer2.py

#!/usr/bin/python3
# -*- coding: utf-8 -*-

from PyQt5.QtCore import QUrl
from PyQt5.QtWidgets import QApplication, QMainWindow, QWidget
from PyQt5.QtWebEngineWidgets import QWebEngineSettings, QWebEngineView
from os import path

class MainWindow(QMainWindow):
    def __init__(self):
        super(QMainWindow, self).__init__()

        self.setWindowTitle("PDF Viewer")
        self.setGeometry(0, 28, 1000, 750)
        self.centralWidget = QWidget(self)

        self.webView = QWebEngineView()
        self.webView.settings().setAttribute(QWebEngineSettings.PluginsEnabled, True)
        self.webView.settings().setAttribute(QWebEngineSettings.PdfViewerEnabled, True)
        self.setCentralWidget(self.webView)

    def url_changed(self):
        self.setWindowTitle(self.webView.title())

    def go_back(self):
        self.webView.back()

if __name__ == '__main__':

    import sys
    app = QApplication(sys.argv)
    win = MainWindow()
    win.show()
    if len(sys.argv) > 1:
        win.webView.setUrl(QUrl(f"file://{sys.argv[1]}"))
    else:
        wd = path.dirname(sys.argv[0])
        test_pdf = "test.pdf"
        win.webView.setUrl(QUrl(f"file://{wd}/{test_pdf}"))
    sys.exit(app.exec_())