Uploading
For students who are having problems with uploaded worksheets being blank, the solution is usually:
Download the worksheet and save it to your computer. Do not open from Moodle and fill in the answers. Open the saved version from your computer. Answer the questions then save it again, maybe even using a different name. See the revised Moodle instructions for suitable pdf programs. The default program for opening PDF doesn't always work. You can also try printing it to PDF, which is another way of saving it. You might also want to do a screenshot. If the other methods don't work, then you can use the screenshot.