Sometimes, a PDF document will take a while time to load. From the course dashboard, check how many pages is included in the document. If the document has multiple pages it's likely that the large file size is impacting the load time. Try refreshing the page to fix the issue.
The PDF is Loading as a Grey Screen
- Right-click on the grey rectangle.
- Click Save As... to download the PDF to your computer.
- Manually mark the lecture as complete.
If you're still having issues, please contact Udemy Support.