All digital files are encrypted for security reasons.
If you are asked for a password it is usually because you have tried to export or save the file with another application, such as Preview or Illustrator. You may also see the password popup when copying and pasting from the guide.
Once you’ve downloaded your guide to your computer, you will still be able to move the file as required. Simple drag and drop the file to the desired location without opening the PDF in any applications!