View pdf document inside a QWidget window

how can I view a pdf document from within a QWidget window

You can use QWebEngineView to view PDF files

#!/usr/bin/env python3

from PyQt6.QtCore import QUrl
from PyQt6.QtWidgets import QApplication, QMainWindow, QWidget
from PyQt6.QtWebEngineWidgets import 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.webView = QWebEngineView()
        self.webView.settings().setAttribute(self.webView.settings().WebAttribute.PluginsEnabled, True)
        self.webView.settings().setAttribute(self.webView.settings().WebAttribute.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:
        test_pdf = "/path/to/your_file.pdf" # change path
        win.webView.setUrl(QUrl(f"file://{test_pdf}"))
    sys.exit(app.exec())

More of my (older) examples for PDF here → GitHub - Axel-Erfurt/Qt5PDFViewer: PDF Viewer with Pyqt5 and pdfjs or QtWebengine · GitHub