Here are some things you should try:

• Be sure to click in the browser frame that contains the document you want to print. If another part of the browser window has the focus, you're likely to only get a blank page from the printer.
• When printing PDFs, use the print button on the Adobe Reader toolbar that floats over the bottom of the document, as shown below. Don't use the browser's File > Print menu.
  
• Sometimes the only way to get a document to print is to save the document to the Windows desktop first. Right click the link to the document, select "Save target as" (or "Save link as") and save the document to the desktop. Then open the document in Acrobat Reader, PowerPoint, etc. and print it.